LANGUAGE FUNCTIONS IN PATIENTS WITH EPILEPSY

Ali Rıza SONKAYA* Zeynep Zeliha BAYAZIT** Mustafa Tansel KENDİRLİ*

*GATA Haydarpasa Training Hospital Department of Neurology

**Ankara University Department of Linguistic and Literature

Abstract. Epilepsy, as a chronic disorder, often impacts cognitive skills including language. A correlation between

language impairment and epilepsy is frequently reported. The neuroanatomical underpinnings of processing

lexical semantics and phonology have been investigated in several clinical and imaging studies but it is

unknown whether this language impairment develops gradually as a consequence of epilepsy or precedes

the onset of seizures. In this research, we administered the ‘Ambiguous Word Test’ to 25 epileptic patients

(12 diagnosed with temporal lobe epilepsy, 8 left-sided, 4 right-sided, and 13 diagnosed with idiopathic

generalized epilepsy) and 40 healthy controls. The test assessed their ability to select the appropriate word

to fill out sentences against alternative words that were phonologically or semantically similar to the correct

option. Patients overall produced significantly more mistakes as compared to controls across conditions.

Characteristically, though, patients with temporal lobe epilepsy exhibited significantly more phonological

mistakes than both patients with idiopathic generalized epilepsy and controls. In particular, phonological

processing of verbs was heavily deteriorated in temporal lobe epileptics, while it was preserved in

idiopathic generalized epileptics. These findings are discussed in the light of relevant neurolinguistic

theories and experimental studies, addressing issues on epilepsy and language that require further

investigation.

Keywords: Language functions, phonology, semantics, ambiguity, epilepsy.

INTRODUCTION

The traditional components of language, phonetics, semantics, and syntax, adequately

characterise the structure of language, but are insufficient to explain the richness of meanings that

arise whenever language is used to communicate. The terms speech and language are sometimes

used as synonyms. However, from a linguistic point of view, they are different sides of the same

coin and are inseparably intertwined. Language refers to the cognitive set-up of the sounds of a

language, the rules for their combination into words and sentences and the meaning behind them.

Speech refers to the articulated utterances and the motor act and ability to perform them. Speech

and language are mainly used for communication and this term also incorporates the use and

understanding of social context and meaning. Language is usually described as consisting of

phonology, which means the set-up of sounds and the rules for their combinations into words. It

also consists of lexicon, meaning the vocabulary of a language and the meaning of words, which

is also referred to as semantics. Additionally it consists of grammar, which refers to the

combination of words into sentences, and pragmatics, which means the social use of language, or

communication.

Researchers from different disciplines have previously focused on different aspects of speech and

language disorders. Linguists have studied specific language functions,neurologists have

interested constructive language functions and psychologists have dealt with explanations

regarding the underlying nature, with particular emphasis on different aspects of cognitive

processing capacity. The etiology of alterations in language, phonological, lexical and semantic

disorders varies and may involve factors such as: organic, intellectual / cognitive, environmental

and emotional which most of the time happens to have an interrelationship among all these

factors (Lemos, Barros & Amorim, 2006). From all of them, it is highlighted the role of epilepsy

which recent studies (Svoboda, 2004) has also emphasized the presence of additional disabilities,

but it is unclear how they are related to speech and language disorders. Interrupted cerebral

activity in epileptic conditions results in disturbances in a variety of cognitive functions and may

also affect speech and language development, but it is not known how epileptiform discharges

contribute to speech and language disorders. Research in the area of speech and language

dysfunctions in patients with epilepsy is scarce and the need for speech and language intervention

has not received much attention (Svoboda, 2004).

Epilepsy, as a chronic disorder, frequently impacts cognitive skills including language (Tuchman,

1994; Besag, 2004). Different types of epilepsy may include impairments in distinct language-

related cortical areas, such as the temporal cortex in temporal lobe epilepsy (Pisano et al., 2005)

and the frontal lobes in idiopathic generalized epilepsy (Meencke, 1985;Hommet et al., 2006).

Previous studies have documented atypical language representation in patients with epilepsy

usually by showing atypical language lateralization (Rasmussen & Milner, 1977; Sabsevitz at

al.,2003;Gaillard et al., 2004; Yuan et al., 2006). However, neurolinguistic research on epilepsy

still lacks insight into particular types of language representation and processing. For example

while the involvement of temporal lobe structures in both semantics and phonology has been

amply studied in the relevant literature (Hagoort, 2005; Indefrey & Cutler, 2005), the effects of

temporal lobe epilepsy on such processes remains poorly investigated.In the few studies

conducted so far, effects of temporal lobe epilepsy have been found on semantic interpretation of

visual input ( Schwarz & Pauli, 2009), as well as on phonological and/or reading processes

(Vanass at al., 2003; Vanass at al., 2005). However, the literature still lacks any systematic

attempts to clarify whether epileptic pathology may selectively affect semantic and/or

phonological processing of particular types of linguistic categories. While the neuroanatomical

foundations of the representation of different grammatical classes (noun/verb) and/or semantic

properties (concreteness/abstractness, entityobject/action) predominantly involve frontal and

temporal cortical areas (Damasio & Tranel, 1993; Cappa & Perani, 2003), neurolinguistic studies

on epilepsy have yet to shed light on such topics. Another characteristic case is that of research on

lexical ambiguity resolution. A complex and dynamic process, it has attracted a significant

amount of considerations (Hogaboam & Perfetti, 1975; Onifer & Swinney, 1981; Glucksberg,

Kreuz, & Rho, 1986; Friederici at al., 1998), as well as several clinical and neuroimaging studies,

overall establishing the involvement of a widespread neural network (Price, 2000). Among others,

this network has been shown to involve the perirhinal, entorhinal, and parahippocampal cortices

within the medial temporal lobe (Schmolck, Stefanacci, & Squire, 2000), as well as left dorsal-

lateral frontal areas, the anterior cingulate and the right inferior parietal lobe (Chan et al., 2004).

The present study was thus designed to address these issues by investigating whether aspects of

semantic and phonological processing forwords of different grammatical classes are impaired in

patients with epilepsies that are not surgically treated. From based on this data, we hypothesized

that patients with epilepsy would exhibit difficulties in processing ambiguous words. On the basis

of the significance of the temporal lobe in the storage of linguistic representations, we also

predicted that patients with temporal lobe epilepsy would demonstrate more profound

impairments in both semantic and phonological aspects of language processing.

MATERIALS AND METHODS

The population included 25 patients with an idiopathic or probably symptomatic form of epilepsy

(11 males, 14 females) attending the Department of Neurology at Ankara University and 40

healthy normal controls (18 males, 22 females). After providing informed consent for the

procedures, which were approved by an institutional review board. All participants were

monolingual native speakers of Turkish.

All patients underwent detailed clinico-electrographic investigations (including 24 h – video

EEG)

as well as a 1.5 T brain MRI scan as part of the diagnostic procedure.With respect to their

intellectual level, intelligence status remains relatively intact in epilepsy. However, mild cognitive

decline, including language and memory impairment, is frequently observed (Motamedi

&Meador, 2003) and is ascribed to biological factors (Meador at al., 2001), psychosocial

parameters (Banos et al., 2004) and anti-epileptic drug treatment (Meador at al., 2003). Patient

entry criteria thus included absence of any other neurological or psychiatric disease, as well as a

Mini-Mental State Examination score exceeding 24 points. The two epileptic groups did not differ

significantly in their scores (Wilcoxon W= 240.5, z = 1.58, p =.07, two-tailed). Patients with

hippocampal sclerosis, but no evidence of dual pathology, were also allowed to participate in the

study.

13 patients suffered from idiopathic generalized epilepsy (IGE). Using the International League

Against Epilepsy diagnostic scheme (Engel & ILAE, 2001), 9 patients were diagnosed with

Juvenile Myoclonic Epilepsy, 4 with IGE with generalized tonic–clonic seizures only, while the

rest suffered from other IGE syndromes not better defined. The remaining 12 patients suffered

from temporal lobe epilepsy. These patients were further subdivided into left (8) and right (4)

temporal lobe epilepsy groups, based on seizure semiology, EEG and MRI criteria. With regard to

etiology, 8 patients suffered from probably symptomatic focal epilepsy and 4 patients had medial

temporal lobe sclerosis. All patients were examined at least 72 h from the occurrence of an

absence, myoclonic, simple or complex partial epileptic seizure (CPS) and at least 7 days from a

primarily (p CTC) or secondarily generalized tonic–clonic seizure (s CTC).

Patients and controls were administered the ‘Ambiguous Word Test’ (Roikou et al., 2003). This

tool

has been previously administered in order to test linguistic functions in healthy subjects and

patients with psychiatric diseases (Kouvatsou et al., 2005; Pita at al., 2003). Subjects were

presented with a set of 45 sentences each missing an ambiguous word (henceforth, the ‘target

word’); the context provided by the sentences from which it was excised sufficed to disambiguate

it: 15 sentences were missing the noun (ambiguous nouns subtest), 15 were missing the verb

(ambiguous verbs subtest) and 15 were missing the adjective (ambiguous adjectives subtest), and

were asked to select the appropriate word among three options, in order to form a meaningful

sentence (Roikou et al., 2003). One of the words had the correct meaning according to context

information, as it was synonymous with the omitted target word with respect to its contextually

appropriate sense (correct choice); another corresponded to an alternative meaning of the target

word, which was, however, incompatible with the context (semantic error); a third onewas

phonologically similar to, but semantically unrelated with the target word (phonological error).

All sentences were presented in a written form. For example, the following sentence was

presented (adapted translation from Turkish):

He has ______ manners.

a) Final (phonological error; contextually inappropriate, but phonologically similar to ‘fine’)

b) Delicate (correct choice; contextually appropriate, semantically similar to ‘fine’)

c) Thin (semantic error; contextually inappropriate synonym of ‘fine’)

According to on our assumption that systematic semantic errors would demonstrate failure in

accessing-retrieving the full range of different senses conveyed by the target word, and/or failure

in inferentially processing contextual information to disambiguate the target word, and/or failure

in sufficiently inhibiting the contextually inappropriate sense of the target word, and/or failure in

sufficiently disinhibiting the contextually appropriate one. Apart from this, systematic

phonological errors would likely exhibit failure in accessing–retrieving the phonological

representation of the lexical morphology of the target word, and/or disruptions in more generic

reading-related processes.

The study employed a 3x 3 x 2 between-subjects design, involving the following independent

variables: Group (3; NC, IGE, TLE), Grammatical Class, based on the three subtests–subsets used

(3;Noun, Adjective, Verb), and Error Type (2; Phonological, Semantic). The dependent measure

was accuracy rates, representing the rate of successful avoidance of phonological and semantic

errors, and thus directly reflecting the extent to which phonological and semantic processing was

shown intact in the particular task. For each condition generated by the factorial crossing of the

above variables, accuracy rates were calculated as follows:

Type A Accuracy = Trialsanswered – Type A Errors

Trialsanswered

RESULTS

Semantic and phonological impairments across grammatical classes

TLEs made more errors overall than NCs (three-way ANCOVA: MSe = .021, p < .005; post-hoc:

NC–TLE: p < .0025, one-tailed; rest of ps, p > .1). In particular, they made more phonological

errors than both NCs and IGEs (MSe=.004, p < .00025; post-hoc: TLE–NC: p < .00025; TLE–

IGE: p < .035, one-tailed; IGE–NC: p > .78), as well as more semantic mistakes than NCs ( MSe

=.035, p < .05; post-hoc: NC–TLE: p < .025, one tailed; rest of ps, p > .5; Fig. 1 below).

Fig. 1. Adjusted mean accuracy rates controlling for the effect of education in semantic and phonological conditions among the three

groups, collapsing over grammatical class. TLEs performed poorer than NCs in semantic conditions. In phonological conditions, TLEs

made more mistakes than both IGEs and NCs. NC: Normal controls; IGE: Idiopathic generalized epileptics; TLE: Temporal lobe

epileptics; NS: Non-significant; *: p < .05; ***: p < .0005; error bars represent ±1 S.E.M.

While TLEs made more errors on verbs than NCs and IGEs across error types (MSe = .002, p < .

005; post-hoc: TLE–IGE: p < .025; TLE–NC: p < .0025, one-tailed; NC–IGE: p > .6), they made

even more phonological mistakes for verbs than the other two groups. Indeed, they made more

phonological mistakes than IGEs across grammatical classes, but significantly even more for

verbs. Similarly, they made more phonological mistakes than NCs across classes (p < .00005), but

even more for verbs ( p < .017). This was verified by one-way ANCOVAs, with TLEs making

significantly more phonological errors for verbs (p < .00000025) than both NCs (p < .000025)

and IGEs (p < .0000025, one-tailed; IGE–NC: p > .35).

Furthermore, IGEs, as compared to NCs, showed spared phonological processing for verbs ( p < .

04). Indeed, while the three grammatical classes did not differ with respect to the phonological

mistakes made by NCs (one-way ANCOVA; p < .005; post-hoc: all ps, p > .4) or TLEs

(Grammatical Class: p > .25), they differed for IGEs, who made significantly less phonological

mistakes for verbs than for adjectives and nouns (one-way ANCOVA; p < .005; post-hoc: verbs–

nouns: p < .035; verbs–adjectives: p< .035, two-tailed; nouns–adjectives: p > .65).

Phonological processing of verbs in IGE and TLE

TLEs showed significantly stronger impairments in processing the phonology of verbs, while

IGEs also showed selectively spared performance in this condition (Fig. 2). The selective nature

of these patterns was revealed with a significant Grammatical Class x Error Type x Group

interaction in a three-way ANCOVA (p < .04). Genuinely, no interaction was observed for

semantic errors, but only for phonological ones (p < .00025).

Fig. 2. Adjusted mean accuracy rates controlling for the effect of Education of the three groups for semantic and phonological types of

errors made for the nouns, adjectives, and verbs subsets of the Ambiguous Word Test. Patients showed lower accuracy rates for the

semantic condition than NCs across grammatical classes. TLEs demonstrated lower accuracy rates for the phonological condition

across grammatical classes than both NCs and IGEs, and even more so for verbs. However, IGEs showed spared performance for

phonological processing of verbs. NS: Non-significant; *: p < .05; ****: p < .00005. Error bars represent ±1 S.E.M.

Inorder to examine laterality effects of TLE, the Group variable was redefined so as to involve

right-, left-TLEs, IGEs, and NCs. Both left- and right-TLEs made more phonological mistakes

than NCs ( MSe = .004, p < .001; post-hoc: left TLE–NC: p < .005; right TLE–NC: p < .03, one-

tailed; rest of ps, p >.25), while only left-TLEs made more semantic mistakes than NCs

(MSe=.018, p<.04; post-hoc: left TLE–NC:p<.03, one-tailed; rest of ps, p>.35).With respect to

the strong phonological disruptions for verbs TLEs showed above, both left- and right-TLEs were

less accurate than NCs and IGEs (MSe=.001, p<.000005; post-hoc: left TLE–NC: p<.0005; left

TLE– IGE: p<.00005; right TLE–NC:p<.017; right TLE–IGE: p<.0025,one-tailed; rest of ps,

p>.9; Fig.3 below).

Fig. 3. Adjusted mean accuracy rates (controlling for the effect of Education) for NCs, IGEs, left-, and right-TLEs for semantic and

phonological conditions, collapsing across grammatical classes. While both left- and right-TLEs show impairments in phonological

conditions, only left-TLEs show significantly more semantic mistakes than NCs. NC: Normal controls; IGE: Idiopathic generalized

epileptics; TLE: Temporal lobe epileptics; NS: Non-significant; *: p < .05; error bars represent ±1 S.E.M.

DISCUSSION

Our results extend findings of previous studies with regard to the impact of epilepsy on semantic

and phonological processing, suggesting that both are disrupted in non-operated patients with

epilepsy. These deficits are shown to pertain to language dysfunction caused by the epileptic

process per se, rather than by surgical excision of brain tissue. In particular, the results

demonstrated more errors for the group of temporal lobe epileptic patients in phonological

aspects of linguistic performance than those produced by idiopathic generalized epileptic patients

and normal controls, across grammatical classes. In addition, epileptic patients demonstrated

significantly poorer performance than the control group in semantic ambiguity resolution, with

stronger disruptions for the temporal lobe epileptic group. Separately, while phonological

processing for verbs was spared for idiopathic generalized patients with epilepsy, it was most

impaired for temporal lobe epileptic patients. Finally, while both left- and right-temporal lobe

patients with epilepsy made more phonological errors than normal healthy controls, only left-

temporal lobe ones made more semantic errors.

Let we begin by saying that lexical ambiguity resolution was deficient in epileptic patients. While

only temporal lobe epileptics exhibited semantic deterioration as compared with normal healthy

controls, idiopathic generalized epileptics did not differ significantly from temporal lobe

epileptics. The findings here are compatible with models incorporating broader fronto-temporal

circuits for lexical semantic processing (Hickok, 2009). Different parts of the left middle and

inferior temporal gyri have been considered crucial for lexical-semantic processing (Hagoort,

2005; Indefrey & Cutler, 2005), and conceptual access mechanisms have been proposed to

primarily involve the lateral posterior temporal lobe (Hickok, 2009).

Furthermore, a replication of the study here with larger sample sizes may also yield significantly

poorer performance for idiopathic generalized epileptics as compared to normal healthy controls.

Semantic information is discussed in the relevant literature as being more distributed in the brain

than phonological information. For idiopathic generalized epileptics, cognitive dysfunction, and

deficits in semantic processing in particular are considered to be quite subtle (Motamedi &

Meador, 2003), with a number of studies indicating that these patients’ performance on several

cognitive tasks lies slightly under normal values (Farwell, Dodrill, & Batzel,1985; Mirsky,

Duncan, & Levav, 2001). Even so, neuropsychological and neuroimaging studies provide

evidence for frontal lobe dysfunction in idiopathic generalized epilepsy (Hommet et al., 2006;

Meencke, 1985). Additionally cognitive functions are well established to involve the mediation of

the frontal, especially prefrontal, cortex (Lezak, 1995). Thereby, as long as the processing and

integration of a lexical meaning into a sentence context heavily involves cognitive functions, a

deficit of the prefrontal cortex may compromise semantic processing (Demb et al., 1995; Faust &

Chiarello, 1998; Fiez, 1997; McDonald et al., 2005).

Patients with temporal lobe epilepsy here showed significant phonological impairments as

compared with both idiopathic generalized epileptics and normal healthy controls. This

corroborates the significance of temporal lobes in phonological processing. Besides, the fact that

both left- and right-temporal lobe epileptics showed these impairments corroborates the idea of

the participation and/or the cooperation of both temporal lobes in phonological processes.

Actually, acoustic and phonological processing has been supported to primarily involve the

superior temporal lobe (and sulcus) bilaterally (Okada & Hickok, 2006;Hickok, 2009).

Activations related to phonological properties are primarily reported for the central to posterior

superior temporal gyrus extending into the superior temporal sulcus (Hagoort, 2005; Indefrey &

Cutler, 2005). A fortiori, the left posterior superior temporal gyrus has been found to participate in

accessing lexical phonology independently of semantic access (Graves at al., 2008). It should be

noted, though, that the findings here cannot dissociate between a more general phonological

(Vanasse et al., 2003) and a more modality-specific reading deficit associated with temporal lobe

epilepsy (Vanasse et al., 2005). Moreover, these findings run contrary to imaging studies on

healthy individuals showing relatively greater activation in frontal regions for phonological as

compared with semantic processing (Billingsley at al.,2001 ).

Interestingly, though, the results here are complementary to and compatible with findings on

types of paraphasias in different epileptic groups. In a study comparing the confrontation naming

ability of dominant, non-dominant temporal lobe epileptic patients, and patients with psychogenic

nonepileptic seizures, it was found that while verbal-semantic paraphasias were similar across

patient groups, phonemic-literal paraphasias were significantly more frequent in dominant

temporal lobe epilepsies (Fargo at al., 2005). Most probably, then, our results here obtain the

equivalent pattern in language comprehension, with phonological deficits occurring selectively

for temporal lobe and not idiopathic generalized epileptic patients, and semantic impairments

occurring for the epileptic patient group as compared to normal healthy controls. Another

interesting case has been obtained by Knott and Marslen-Wilson (2001), who examined an

amnesic patient with medial temporal lobe damage: theirword span performancewas normal, yet

their supraspan recall was characterized by a distinctive pattern of phonological errors, where

they recombined phonemes fromthe original list to form newresponsewords, similar-sounding to

the original ones (e.g. ‘life tramp’). These errors closely resemble the phonological ones made by

both right- and lefttemporal lobe epileptics here, as compared to both idiopathic generalized

epileptics and normal healthy controls. Consciously our findings support that phonological

processing of verbs was selectively spared for idiopathic generalized epileptics, while it was most

strongly deteriorated in temporal lobe epileptics, both right- and left-sided. This pattern would

consistent with the idea that phonological processing of verbs basically relies on temporal lobe

structures, in contrast to semantic properties of verbs, which are held to rely on frontal cortical

areas (Damasio & Tranel, 1993;Cappa & Perani, 2003). Presumably, this may be ascribed to the

high complexity of morphology-to-phonology mappings involved in processing verbs. In Turkish,

morphological features of person, number, mood, tense, voice, and aspect are phonologically

instantiated in verbs, whereas nouns and adjectives involve mappings for case. Such heavy load

in processing the phonology of verbs may thus require intact temporal cortical areas for the

efficient application of such mappings – otherwise, the computational burden of retrieving the

correct morphological information for processing verbs would compromise the retrieval of the

correct lexical form.

With respect to the laterality of the observed failures, patients with left temporal lobe epilepsy

made more semantic mistakes than normal healthy controls, while both temporal lobe epileptic

groups made more phonological errors. This is inherently the reverse pattern of that demonstrated

in other researches, where more phonological mistakes are stated in left temporal lobe epilepsy,

while semantic mistakes are encountered both in left and right temporal lobe epilepsy (N’Kaoua

at al., 2001). While several neuropsychological studies have genuinely attributed separate roles to

each cerebral hemisphere in semantic ambiguity processing (Zaidel et al., 1995; Federmeier &

Kutas, 1999; Coney & Evans, 2000; Grindrod & Baum, 2005), it has been also suggested that

both hemispheres play similar roles (Zempleni at al., 2007). In view of the small number of

participants, especially for the right-temporal lobe epileptic patient group, the non-selective

nature of the findings here does not allow us to further discuss the significance of laterality effects

of temporal lobe epilepsy in language processing (Schwarz & Pauli, 2009; Yucus & Tranel,

2007). However, it is worth noting that there have been previous, unexpected findings of

linguistic impairments for right-, and not left-temporal lobe epileptic patients (Billingsley et al.,

2001). Finally, another limitation of the present study to consider in the context of further

experimentation would be the absence of overt matching of normal healthy controls with patients

in measures of intellectual level. For the present study, the level of education was factored in as a

between-subjects variable to minimize any confounds with the group variable, while both patient

groups here scored above average in a mini-mental state examination.

CONCLUSION

Our study evidence was provided for the involvement of temporal lobe epilepsy in phonological

processing, with particular reference to verbs, as well as for the impact of epilepsy on semantic

processing, examined here in the process of lexical ambiguity resolution. The results support a

very significant role of bilateral temporal lobe structures in phonological processes, with more

complex morpho-phonological mappings, such as those of verbs, relying more on those

structures. These findings should optimally be replicated with more diligently matched subject

groups in intellectual and education level, and any marginal effects found here remain to be

further explored.

REFERENCES

Banos, J. H., LaGory, J., Sawrie, S., Faught, E., Knowlton, R., Prasad, A., et al. (2004). Self-report of cognitive abilities in temporal lobe epilepsy: cognitive, psychosocial, and emotional factors. Epilepsy & Behavior, 5(4), 575–579.

Besag FM.(2004) Behavioral aspects of pediatric epilepsy syndromes. Epilepsy Behav,5(Suppl 1):S3–S13.

Billingsley, R. L., McAndrews, M. P., Crawley, A. P., & Mikulis, D. J. (2001). Functional MRI of phonological and semantic processing in temporal lobe epilepsy. Brain, 124(6), 1218–1227.

Cappa, S. F., & Perani, D. (2003). The neural correlates of noun and verb processing. Journal of Neurolinguistics, 16(2–3), 183–189.

Chan, A., Liu, H., Yip, V., Fox, P., Gao, J., & Tan, L. (2004). Neural systems for word meaning modulated by semantic ambiguity.NeuroImage, 22, 1128–1133.

Coney, J., & Evans, K. (2000). Hemispheric asymmetries in the resolution of lexical ambiguity. Neuropsychologia, 38, 272–282.

Conover, W. J. (1999). Practical nonparametric statistics (3rd ed.). Wiley.

Damasio, A. R., & Tranel, D. (1993). Nouns and verbs are retrieved with differently distributed neural systems. Proceedings of the National Academy of Sciences, 90, 4957–4960.

Demb, J., Desmond, J., Wagner, A., Vaidya, C., Glover, G., & Gabrieli, J. (1995). Semantic encoding and retrieval in the left inferior prefrontal cortex: a functional MRI study of task difficulty and process specificity. Journal of Neuroscience, 15, 5870–5878.

Engel, J., Jr., & International League Against Epilepsy (ILAE). (2001). A proposed diagnostic scheme for people with epileptic seizures and with epilepsy: report of the ILAE task force on classification and terminology. Epilepsy, 42, 796–803.

Fargo, J. D., Schefft, B. K., Dulay, M. F., Privitera, M. D., & Yeh, H.-S. (2005). Confrontation naming in individuals with temporal lobe epilepsy: a quantitative analysis of paraphasic error subtypes. Neuropsychology, 19(5), 603–611.

Farwell, J., Dodrill, C., & Batzel, L. (1985). Neuropsychological abilities of children with epilepsy. Epilepsia, 26, 395–400.

Faust, M., & Chiarello, C. (1998). Sentence context and lexical ambiguity resolution by the two hemispheres. Neuropsychologia, 36(9), 827–835.

Federmeier, K. D., & Kutas, M. (1999). Right words and left words: electrophysiological evidence for hemispheric differences in meaning processing. Cognitive Brain Research, 8, 373–392.

Fiez, J. (1997). Phonology, semantics and the role of the left inferior prefrontal cortex. Human Brain Mapping, 5, 79–83.

Friederici, A., Steinhauer, K., Mecklinger, A., & Meyer, M. (1998).Working memory constraints on syntactic ambiguity resolution as revealed by electrical brain responses. Biological Psychology, 47, 193–221.

Gaillard WD, Balsamo L, Xu B, et al.(2004) fMRI language task panel improves determination of language dominance. Neurology,63:1403–8.

Glucksberg, S., Kreuz, R. J., & Rho, S. (1986). Context can constrain lexical access: implications for models of language comprehension. Journal of Experimental Psychology: Learning, Memory and Cognition, 12, 323–335.

Graves, W. W., Grabowski, T. J., Mehta, S., & Gupta, P. (2008). The left posterior superior temporal gyrus participates specifically in accessing lexical phonology. Journal of Cognitive Neuroscience, 20(9), 1698–1710.

Grindrod, C., & Baum, S. (2005). Hemispheric contributions to lexical ambiguity resolution in a discourse context: evidence from individuals with unilateral left and right hemisphere lesions. Brain and Cognition, 57, 70–83.

Hagoort, P. (2005). On Broca, brain, and binding: a new framework. Trends in Cognitive Sciences, 9(9), 416–423.

Hickok, G. (2009). The functional neuroanatomy of language. Physics of Life Reviews, 6, 121–143.

Hogaboam, T. W., & Perfetti, C. A. (1975). Lexical ambiguity and sentence comprehension. Journal of Verbal Learning and Verbal Behavior, 14, 265–274.

Hommet, C., Sauerwein, H., De Toffol, B., & Lassonde, M. (2006). Idiopathic epileptic syndromes and cognition. Neuroscience and Biobehavioral Reviews, 30(1), 85–96.

Indefrey, P., & Cutler, A. (2005). Prelexical and lexical processing in listening. In M. S. Gazzainga (Ed.), The cognitive neurosciences (pp. 759–774). MIT Press.

Knott, R., & Marslen-Wilson, W. (2001). Does the medial temporal lobe bind phonological memories? Journal of Cognitive Neuroscience, 13, 593–609.

Kouvatsou, Z., Pita, R., Kimiskidis, V., Kazis, D., Lazaridou, E., Papagiannopoulos, S., et al. (2005). Lexical ambiguity in epilepsy. Epilepsia, 46(6),153.

Lemos MES, Barros CGC, Amorim RHC.(2006) .Representações familiares sobre as alterações no desenvolvimento da linguagem de seus filhos. Distúrbios da Comunicação,18(3):323-33.

Lezak, M. (1995). Neuropsychological assessment. NY: Oxford University Press.

McDonald, C., Bauer, R., Filoteo, J., Grande, L., Roper, S., Buchanan, R., et al. (2005). Semantic priming in patients with right frontal lobe lesions. Journal of the International Neuropsychological Society, 11(2), 132–143.

McSweeney, M., & Porter, A. C. (1971). Small sample properties of nonparametric index of response and rank analysis of covariance.

Occasional paper No. 16. East Lansing, Michigan: Office of Research Consultation. Michigan State University.

Meador, K. (2002). Cognitive outcomes and predictive factors in epilepsy. Neurology, 58(5), S21 S26.

Meador, K., Gilliam, F., Kanner, A., & Pellock, J. (2001). Cognitive and behavioral effects of antiepileptic drugs. Epilepsy and Behaviour, 2(4), SS1–SS17.

Meencke, H. J. (1985). Neuron density in the molecular layer of the frontal cortex in primary generalized epilepsy. Epilepsia, 26, 450–454.

Mirsky, A., Duncan, C., & Levav, M. (2001). Neuropsychological studies in idiopathic generalized epilepsies. In I. Jambaque, M. Lassonde, & O. Dulac (Eds.), Neuropsychology of childhood epilepsy (pp. 141–149). NY: Plenium Press.

Motamedi, G., & Meador, K. (2003). Epilepsy and cognition. Epilepsy and Behaviour, 4(2), S25–S38.

N’ Kaoua, B., Lespinet, V., Barsse, A., Rougier, A., & Claverie, B. (2001). Exploration of hemispheric specialization and lexicosemanticprocessing in unilateral temporal lobe epilepsy with fluency tasks. Neuropsychologia, 39, 635–642.

Okada, K., & Hickok, G. (2006). Identification of lexical-phonological networks in the superior temporal sulcus using functional magnetic resonance imaging. Cognitive Neuroscience and Neuropsychology, 17(12), 1293–1296.

Onifer, M., & Swinney, D. A. (1981). Accessing lexical ambiguities during sentence comprehension: effects of frequency of meaning and contextual bias. Memory and Cognition, 15, 225–236.

Pisano, T., Marini, C., Brovedani, P., Brizzolara, D., Pruna, D., Mei, D., et al. (2005). Abnormal phonologic processing in familiallateral temporal lobe epilepsy due to a new LGII mutation. Epilepsia, 46(1), 118–123.

Pita, R., Lazaridou, L., Kandylis, D., Kaprinis, S., & Kaprinis, G. (2003). The development of the chronic schizophrenics’ perceptionof ambiguous words through the process of their psychosocial adjustment. 20–23/11/2003 1st International Congress on Brain and Behaviour, Thessaloniki.

Price, C. (2000). The anatomy of language: contributions from functional neuroimaging. Journal of Anatomy, 197, 335–359.

Rasmussen T, Milner B.(1977) The role of early left-brain injury in determining lateralization of cerebral speech functions. Ann NY Acad Sci,299:355 69.

Roikou, K., Pita, R., Kiosseoglou, G., Gioulis, P., Bozikas, V., & Karavatos, A. (2003). The perception of ambiguous words in patientswith schizophrenia. Engefalos, 40(3), 99–104.

Sabsevitz DS, Swanson SJ, Hammeke TA, Spanaki MV, Possing ET, Morris GL, Mueller WM, Binder JR.(2003). Use of preoperative functional neuroimaging to predict language deficits from epilepsy surgery. Neurology , 60:1788–1792.

Schmolck, H., Stefanacci, L., & Squire, L. (2000). Detection and explanation of sentence ambiguity are unaffected by hippocampallesions but are impaired by larger temporal lobe lesions. Hippocampus, 10, 759–770.

Schwarz, M., & Pauli, E. (2009). Postoperative speech processing in temporal lobe epilepsy: functional relationship betweenobject naming, semantics and phonology. Epilepsy & Behavior, 16(4), 629–633.

Svoboda, W. B. (2004) Childhood epilepsy, language, learning, and emotional complications, Cambridge, UK ; New York, Cambridge University Press.

Tuchman RF.(1994). Epilepsy, language, and behavior: clinical models in childhood. J Child Neurol;9:95–102.

Vanasse, C. M., Béland, R., Jambaqué, I., Lavoie, K., & Lassonde, M. (2003). Impact of temporal lobe epilepsy on phonological processing and reading: a case study of identical twins. Neurocase, 9, 515–522.

Yuan W, Szaflarski JP, Schmithorst VJ, et al. (2006). fMRI shows atypical language lateralization in pediatric epilepsy patients. Epilepsia,47:593–600.

Yucus, C. J., & Tranel, D. (2007). Preserved proper naming following left anterior temporal lobectomy is associated with early age of seizure onset. Epilepsia, 48(12), 2241–2252.

Zaidel, D., Zaidel, E., Oxbury, S., & Oxbury, J. (1995). The interpretation of sentence ambiguity in patients with unilateral focalbrain surgery. Brain and Language, 51, 458–468.

Zempleni, M., Renken, R., Hoeks, J., Hoogduin, J., & Stowe, L. (2007). Semantic ambiguity processing in sentence context: evidence from event-related fMRI. NeuroImage, 34(3), 1270–1279.