The beginning of modern neuropsychology inthe second half of the XIX century was intimatelyrelated with neuroanatomy. In multi-componentmodels of language and verbal cognition thefunctional psychological architecture had a precisecorrespondence with the neurological structure, atthe level of cerebral areas, and their connections bywhite matter fibre tracts. A canonical example isWernicke’s model of language, where “centres” (ofauditory memory images of words, of motormemory images of words, etc.) have correlates inspecific cortical areas of the brain, connected bywhite matter pathways (De Bleser and Luzzatti,1989).

The issue discussed here concerns the relevanceto our understanding of human cognition of theview that cognitive components have discreteanatomical correlates, that is to say, that there is acorrespondence, at a given level of description,between the neuroanatomical and the cognitivearchitectures. An alternative view, which has beeninfluential among cognitive neuropsychologists fora number of years, is that, although the brainprovides the main physical basis for mentalactivity, the levels of description of psychology andbiology (with neuroanatomy being the particularbiological level of interest here) are too differentand far removed, to allow a fruitful cross-fertilization (discussion in Vallar, 2000). Here, Ishall consider neuroanatomy mainly in terms of thecartography of brain regions and their connections(as highly relevant as it is, the evidence fromfunctional neuroimaging and neurophysiology isnot discussed).

Neuroanatomical data may adjudicate betweencompeting theories of mental activity. To illustratethis view, and to make the argument moreconvincing, I shall make use first of all of anexample, which is not a recent finding,representing instead established, and now widelyaccepted, evidence.

In the late 1960s the functional organization ofhuman memory was controversial. One traditionalview was that memory is basically unitary. Thecompeting position (based on behaviouralphenomena such as short-term forgetting, digitspan, and the recency effect in free recall) was thata distinction should be drawn between short-termand long-term components. At the behavioural

level, there was empirical evidence supportingeither view. The single more convincing crucialdata came from the domain of neuropathology,with the observation that bilateral damage to aspecific region of the brain (the medial temporallobe) brought about a selective deficit of long-termmemory (global amnesia), with patients showing anentirely preserved performance in tasks putativelyassessing short-term memory (Atkinson andShiffrin, 1968). A few years later, this dissociationwas complemented by the finding that damage to adifferent region of the brain (the left inferiorparietal lobule, IPL) may impair auditory-verbal(phonological) short-term memory (Vallar andPapagno, 2002).

Box-and-arrows models of cognition andneuroanatomy. In models developed in the XIXcentury, such as Wernicke’s model of language, thecorrespondence of the multi-componentorganization of mental functions with brain areasand their connections was conceived as point-to-point. At present, the correspondence should bebetter seen in terms of cortico-subcortical notoverlapping, though interacting, circuits, whichsupport discrete mental functions. An illustrativeexample is provided by phonological (auditory-verbal) short-term memory . This system, originallyconsidered unitary, has further fractionated into aphonological short-term store, and a rehearsalsystem, whose neural bases include thesupramarginal gyrus of the IPL, and the premotorcortex [Brodmann’area (BA) 44 (Broca’s area), BA6) in the left hemisphere (Vallar and Papagno, inpress; Vallar et al., 1997). Functionally, the processof rehearsal is closely related to the phonologicalshort-term store: one main activity of rehearsalmay be described as the reviving of the memorytrace held in the phonological store, preventing itsdecay. Anatomically, white matter tracts, such asthe arcuate fasciculus, may support the interactionbetween the rehearsal process (left premotorcortex) and the phonological store (left IPL) (seefigure 1).

The anatomo-functional model shown in figure1 concerns phonological short-term memory. Thearea involved, however (BA 44, BA 6, thesupramarginal gyrus in the IPL) are componentparts of the language areas in the left hemisphere.The functional model mapped onto these brain

Cortex, (2004) 40, 223-225

FORUMNEUROANATOMY OF COGNITION, NEUROANATOMY AND COGNITION

Giuseppe Vallar

(Dipartimento di Psicologia, Università degli Studi di Milano-Bicocca)

regions may also be the classical Wernicke-Geschwind model of language (see a modernversion in Dronkers et al., 2000). The significance,in terms of the neural correlates of cognitiveprocesses, of a given set of cerebral regions andtheir connections is therefore closely related to thetype of functional description or model of interest(e.g., Wernicke’s model of language, thephonological short-term memory component ofworking memory).

The localization of a cognitive process in aparticular brain region may also have implicationsconcerning its functional properties. Thelocalization of verbal rehearsal in the premotorcortex of the left hemisphere suggests output-related features. Rehearsal may be conceived asmaking use phonological systems primarily

concerned with the articulatory pre-motor planningof speech. This view differs from competinginterpretations in terms of a specific system solelysupporting immediate retention in the phonologicalshort-term store. Also the suggestion of a moreperipheral process, involving the articulatorymusculature, is made unlikely.

To summarize, knowledge about theneuroanatomical organization of the brain (at thelevel of assemblies of neural cells and theirconnections) provides the fundamental cartographyfor describing the neural basis of cognition interms of networks of interconnected cortical andsubcortical regions. In addition, knowledgeconcerning the neuroanatomical instantiation ofcognitive systems offers information relevant to ourunderstanding of their functional architecture, forinstance making some functional accounts lessplausible than others.

A concluding caveat. These selected pieces ofevidence suggest that neuroanatomical data providethe cartography onto which functional architecturesmay be mapped. Neuroanatomical data bythemselves, however, include limited informationas to the functional (behavioural in this discussion)significance of connections among cerebral regions,and of the resulting networks. One specificproblem in this respect may arise from the fact thatconnections among cerebral regions are oftenhighly redundant, so that a cerebral area istypically connected with many others.

One illustrative example: Vallar (1993),reviewing the localization of the lesion in patientswith left neglect and damage to the right thalamus,suggested that the posterior part of it, including thenucleus pulvinar, is frequently involved. Vallar(1993), on the basis of the well-known associationbetween neglect and cortical damage to the rightIPL, argued that a network including the pulvinarand the IPL in the right hemisphere contributed tospatial representation and attention.Neuroanatomical support to this conclusion isprovided by the existence of important connectionsbetween these two regions, via the posterior limb ofthe internal capsule. More recently Karnath et al.(2002) confirmed the association between neglectand damage to the right pulvinar. With reference tothe recent suggestion that damage to the superiortemporal gyrus (STG) plays a main role in spatialneglect (Karnath, 2001), they emphasized thefunctional role of pulvinar-STG connections. As tothe basal ganglia (putamen and caudate nucleus), asimilar line of reasoning led Karnath et al. (2002) toemphasize the striatal connections with the STG,rather than those with the IPL (for cortico-subcortical connections see, e.g., Makris et al., 1999;Yeterian and Pandya, 1993, 1998). From ananatomical standpoint, the quantitative amount ofthese diverse connections may be an important,though not unique, factor in determining theirfunctional relevance.

224 Giuseppe Vallar

Fig. 1 – An anatomofunctional model of phonological short-term memory. Auditory-verbal material, after early acoustic andphonological analysis enters the main retention component of thesystem, the phonological STS, where material is coded in aphonological format. The phonological STS is an input-system, towhich auditory material has a direct and automatic access. Theprocess of rehearsal is conceived as involving a recirculation ofthe memory trace between the phonological STS and aphonological output system, the phonological output buffer orphonological assembly system, primarily concerned with thearticulatory programming of speech output, with a recurringtranslation between input (acoustic) and output (articulatory)phonological representations.

In conclusion, from the vantage point of thecognitive neuroscientist, neuroanatomy may be metaphorically seen as a map, with the functionalmeaning of its component parts being derivedthrough a range of data sets with a behaviouralcomponent, from the domains of neuropsychology,neurophysiology, and functional neuroimaging.

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Giuseppe Vallar, MD, Dipartimento di Psicologia, Edificio U6, Università degli Studidi Milano-Bicocca, Piazza dell’Ateneo Nuovo 1, 20126-Milano Italia,giuseppe.vallar@unimib.it

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