Cortical Lesions

Question 1

Understand the role the frontal, temporal, parietal, and occipital lobes in human cognition

Answer 1

Frontal Lobe: Voluntary movement, language fluency (L side), motor prosody (R side), comportment, executive function, and motivation.

Parietal lobe: tactile sensation, visuospatial function (R), Attention (R), Reading (L), Writing (L), Calculation (L).

Temporal Lobe: language comprehension (L), sensory prosody (R), Memory, emotion.

Occipital Lobe: vision, visual perception, visual recogniton.

Question 2

Appreciate the three major frontal lobe syndromes

Answer 2

1) . Disinhibition – from orbitofrontal lesions
* disorder of comportment when a person can no longer adequately integrate limbic drives into appropriate behavioral repertoire.
* Irritability, loss of empathy, impulsivity, hypersexuality, hyperphagia, and violence.

2) . Exective dysfunction – dorsolateral prefrontal lesions
* no longer have capacity to plan, carry out, and monitor sequential goal-directed action.
* Also lack perserveration – altering actions in response to changing environmental stimuli

3) . Apathy: medial frontal lesions
* Lack of motivation.
* Most severe forms are abulia and akinetic mutism

Question 3

Recognize the major cognitive disorders related to temporal lobe lesions

Answer 3

1) . Wernicke’s Aphasia: auditory comprehension is impaired because of a lesion n post. region of L superior temporal gyrus (Wernicke’s area, Brodmann area 22).
2) . Sensory aprosody: diminished ability to comprehend emotional inflection of speech due to lesion in R hemisphere analogue of Wernicke’s area.
3) . Amnesia and memory: hippocampus is essential for new learning. Only remove 1 hippocampus not both during surgery.

4) . Emotion: basic emotions of flight/fight, feeding, and sexuality as mediated by limbic system from connections between temporal lobe and diencephalon.
* Temporal lobe epilepsy: temporolimbic lesion of temporocortical region affecting emotion. Commonly caused by epilepsy lesions in the brain causing lasting personality changes and a deepened emotionality.

Question 4

Understand the syndrome of hemineglect as a prototype parietal lobe syndrome

Answer 4

Hemineglect: failure to report, respond to, or orient to sensory stimuli that can not be explained by primary sensory dysfunction. Inattention to one side of the body or extrapersonal space.

• Common after lesion to R hemisphere (dominant for attention).
• L hemineglect: disabling disorder of cognition.

Question 5

Know the difference between visual field deficits and visual agnosia

Answer 5

Occipitoparietal: dorsal stream, tells “where” in visual system
Occipitotemporal: ventral stream, tells “what” something is in the visual stream.

Visual field deficits: absence of vision!!! So actually UNABLE to physically see something.

Visual agnosia: visual image is seen normally, but your brain can’t recognize it (recognition deficit).
•Object agnosia: from L occipitotemporal lesions – can’t understand what something is.
•Face agnosia: (prosopagnosia) from R occipitotemporal lesions., no idea who people are.
•Simultagnosia: from bilateral occipitotparietal lesions, can’t recognize the entirety of a visual array, so have no idea where things are or how to process a location.