it doesn’t take a lot of brains to understand the brain ...bridgesnky.org/public/phifer...
TRANSCRIPT
1
It Doesn’t Take A Lot of
Brains to Understand the
Brain: Functional
Neuroanatomy Made
Ridiculously Simple
James F. Phifer, Ph.D.
Clinical Neuropsychologist
6th Annual Northern Kentucky TBI Conference March 23, 2012 www.bridgesnky.org
Objectives
1) A simple model for understanding the
relationship between the location of a
brain injury and the resulting changes in
thinking, emotions, language, and
behavior is presented
2) Essential distinctions between the
functions of the right vs. left hemispheres
and the anterior vs. posterior aspects of
the brain are presented.
Objectives
3) Common symptoms of left brain
dysfunction are presented.
4) Common symptoms of right brain
dysfunction are presented.
5) Changes in emotional functioning with
right vs. left brain dysfunction are
discussed.
Functional Anatomy of Brain
Anterior – Output/Efferent/Motor
Posterior – Input/Afferent/Sensory
Left
detail-oriented, sequential, step-by-step,
temporal
Right
Contour, big-picture, simultaneous
relationships, spatial
Left Brain Dysfunction
Language is composed of sequences of details (e.g., united vs. untied)
Language Disorders
Broca’s aphasia – slow, effortful, decreased fluency
Wernicke’s aphasia – fluent paraphasic jargon, impaired comprehension
Apraxia – inability to perform learned motor sequences
2
Left Brain Dysfunction Decreased attention to detail
Impaired sequencing ability
Impulsive, globalistic reasoning
Dyscalculia
Gerstmann’s syndrome Dyscalculia
R-L confusion
Dysgraphia
Impaired graphesthesia
Finger agnosia
Predisposed to Depression/Anxiety/
Pessimism/Negativity
Right Parietal Lobe
Center for integrating somatic sensory
information with visual and auditory
information, for the purpose of
constructing an awareness of the body
(schema) and its relation to extra-personal
space
Right Brain Dysfunction
Topographical Disorientation
Impairment of cognitive “maps”
Difficulty understanding and recalling
relationships among places
Agnosia
Lack of recognition of familiar objects
perceived by the senses – color, angle of
orientation, edge, motion cues are utilized in
form discrimination
Right Brain Dysfunction
Agnosia
Prosopagnosia – impaired facial recognition
Environmental agnosia – inability to recognize familiar
places
Visual Object agnosia – inability to recognize
common objects
Flat Affect, Dimunition of emotional responsivity
Aprosodia
inability to comprehend or produce emotional
component of speech
3
Right Brain Dysfunction
Constructional Apraxia
Hyperattention to Detail
Neglect of “big picture,” larger perspective
Task Impersistence
Failure to carry tasks through to completion
Predisposed to Apathy/Indifference to
Threat/Failure
Unilateral Neglect Defined
Failure to report, respond, or orient to
novel or meaningful stimuli presented to
the side opposite a brain lesion (Heilman,
1979)
Failure cannot be attributed to either
sensory or motor deficits
What do these patients look
like? May:
Bump wheelchairs into left side of doorway / forget to lock and/or unlock brakes of wheelchair
Fail to locate or eat food on left side of plate
In dressing, may not put left arms (for right side brain lesion) through left sleeves or put left socks and shoes on
May shave or make-up only the right side of the face
Not read words on left side of page
Patients pose a considerable challenge for rehabilitation professionals
Sitting posture of patient with
unilateral neglect
PATIENT DRAWINGS
5
4
Drawing a Clock Writing Text
Characteristics of Unilateral
Neglect Most common with
right hemisphere
lesions
Usually associated
with lesions of the
parietal lobe
Features of USN Hemi-inattention (1/2 of universe ceases to exist)
Extinction on bilateral simultaneous stimulation
Right gaze preference
Denial of disability (anosognosia); e.g., driving
Hemialexia/Hemiagraphia
Asomatognosia: failure to recognize own limb (“Get this baby off my knee”; “There’s a wild animal in my bed”)
Motor neglect – failure to use left extremity
Allesthesia – mislocation of stimuli to right side; e.g., “circling” effect
Attentional Theories of Neglect
Relationship between a photograph and
total visual space is analogous to the
complex relationship between the contents
of awareness and the vast quantities of
available information
“Attention” refers to the neural
mechanisms that select the part of
stimulus space that is to capture the
center of awareness
5
Attentional Theories of Neglect
Attention is a composite of two major operations (Mesulam, 1985):
1) Matrix or “tone” function: concerns sensitivity or regulation of overall information processing capacity, detection efficiency
2) Vector or channel function – concerns direction and target of attention in any one of behaviorally-relevant spaces (e.g., body space, extrapersonal space, mnemonic, visceral)
USN as a Disorder of Directed
Attention An important vector aspect of attention is the ability to direct the focus of awareness toward behaviorally-relevant sensory events in extrapersonal space;
“It can be concluded that unilateral neglect is not a deficit of seeing, hearing, feeling, or moving, but one of looking, listening, touching, and searching. It appears that this phenomenon represents a fundamental disturbance in a vector aspect of attention - namely, in the spatial distribution of directed sensory attention” (Mesulam,
1985, pp. 141-142)
Why is left neglect more
common than right? Right hemisphere is dominant for directed sensory attention and contains the neural apparatus for attending to both sides of space;
Left hemisphere is exclusively concerned with contralateral right hemispace;
Left hemisphere lesions are unlikely to yield neglect since the intact right hemisphere can attend to right hemi-space. Right hemisphere lesions, on the other hand, will result in left neglect, since the intact left hemisphere lacks the neural mechanisms for ipsalateral attention.
Attentional Differences in the
Hemispheres of the Brain Perceptual Aspects of Neglect
Sensory events in right hemi-space have excessive impact on awareness (“right pull”)
Posner (1984) showed patients with left USN have excessive difficulty disengaging attention from targets in right hemi-space
One mechanism of neglect is abnormal magnetism exerted by right-sided stimuli
6
Psychobiology of Affect Two separate systems exist in brain for modulating affect
a. Positive affect - sense of enthusiasm,
happiness, joy
b. Negative affect - sadness, distress, anxiety
You don’t need to be sad to be depressed;
Per DSM-IV, depression may be related to either:
a. persistent low mood or
b. diminished interest or pleasure in usual activities
3/10/2012 *
Psychobiology of Affect
Positive affect is related to mesolimbic
“pleasure” pathways, with control centers
in left frontal lobe
Negative affect is related to “pain”
pathways of periaqueductal gray area,
with control centers in right frontal lobe
3/10/2012 *
Post-TBI/CVA Depression
Normally there is a balance between
Positive and Negative Affect - to avoid
being too happy (mania) or too sad
(depressed)
Left frontal lesion disrupts balance,
resulting in a lack of inhibition of Negative
Affect
Right hemisphere lesion associated with
flattening of emotionality which insulates
from depression
3/10/2012 *
Psychobiology of Affect On fMRI studies (Davidson, 1995),
individuals with extreme left-side activation
rated themselves as strong, enthusiastic,
proud, excited, while those with extreme
right-side activation viewed themselves as
distressed, scared, nervous
Psychobiology of Affect
Kenworthy (1992) played tapes of positive
and negative emotional sounds to pts with
right or left hemispheric epilepsy
Left hemisphere patients described
positive sounds (e.g., baby cooing) in
negative manner (“maybe it’s in danger”)
Right hemisphere patients were under-
stimulated and under-concerned (heard
woman scream, assumed not in trouble
Psychobiology of Affect
Explains why left brain patients are at risk
for suicide and depression, while right
brain patients check out of rehab early –
underestimate their deficits and are overly
optimistic. They think “Yes, I can’t walk or
use my left arm, but I’ll get better.”
7
Psychobiology of Affect
Right frontal activation associated with
vigilance to threat-related cues, anxiety
Decreased right frontal activity associated
with inability to experience emotional
consequences of punishment