Temporal and Occipital Lobe Lesions

Temporal Lobe

contains limbic structures including the hippocampus, amygdala, auditory cortex and Meyer’s Loop

Amygdala gets all sensory info

Functions:

processes auditory information

contains Limbic System "Papez’s Circuit": connection of cortex with hypothalamus; hypothalamus (mammillary bodies)

Þ anterior nucleus of dorsal thalamus Þ cingulate gyrus (cortex) Þ parahippocampal gyrus Þ hippocampus Þ fornix Þ hypothalamus

cortical control of emotional expression

links sensory information with auditory and visual object recognition, emotional responses, and establishes importance of sensory information

temporal-occipital cortex – color and object recognition

Wernicke’s Area – posterior superior left temporal lobe; processes visual and auditory information and is essential for understanding written and spoken language

Meyer’s Loop – carries information from superior visual field

Either Right or Left Temporal Lobe Damage – contralateral superior quadrantanopia

Right Temporal Lobe Damage

hippocampus damage: impaired spatial memory and recollection of music

bilateral injury results in severe short term memory loss and inability to form new memory Þ i.e., H.M.

posterior superior temporal lobe damage: impaired ability to recognize emotional content of language (Receptive Aprosodia)

auditory cortex damage: compromised appreciation and understanding of music

auditory cortex and hippocampus damage: severely compromised music ability and recollection of music

prosopagnosia: inability to recognize faces

Left Temporal Lobe Damage

hippocampus – impaired verbal memory
Wernicke’s Aphasia – profound language deficit (see later)

Bilateral Temporal Lesions

auditory agnosia – inability to distinguish sounds

profound inability to form new memory Þ anterograde amnesia

Occipital Lobe – primary visual processing center

Occipital lobe alone

Function: processes information about contralateral visual world

Damage: contralateral visual defect

Occipital-parietal lobe

Function: visual, spatial orientation

Damage:

1. inability to tract objects in opposite visual field

2. ß significance of objects in contralateral field

3. Visual hallucinations

Temporal-occipital lobe

Function: color and object recognition

Occipital-parietal-temporal lobe

Function: complex visual, spatial integration

Damage: Balint’s Syndrome (ocular motor apraxia – inability to direct hand movement under visual guidance)

Clinical Evaluation of Language Function

Spontaneous language production

(1) Nonfluent aphasia
(2) Fluent aphasia
(3) Mutism
(4) Articular disorders
(5) Other nonphasic disorders of production

Repetition

Comprehension of Language

Other Language Signs

(1) Writing
(2) Comprehension of written language
(3) Naming

Emotional changes

Other neurological signs – particular hemiparesis, visual field defects

Types of Aphasia

(1) Broca’s Aphasia – Non Fluent Aphasia

Impaired speech: slow rate, irregular rhythm, telegraphic content, slow articulation
Writing poor: impaired penmanship, leave out grammatical words
Repetition is impaired
Telegraphic speech and writing: omit articles and connectives

Comprehension and naming spared

Associated Findings: right hemiparesis; patient frustration due to awareness of deficit
Localization: Broca’s Area (inferior posterior frontal gyrus)

(2) Wernicke’s Aphasia – Fluent Aphasia

Impaired speech: fluent but little content, paraphasic errors(incorrect use of words/phrases), neologisms(nonexistant words)
Impaired writing: penmanship preserved, little content with incorrect subjects and objects, paraphasic errors, neologisms
Repetition: impaired with output similar to that of spontaneous speech and writing

Comprehension: markedly impaired; will give affect of understanding, but output shows impaired understanding
Naming: paraphasic or no response
Associated Findings: right homonymous hemianopsia, or superior quadrantanopsia
Localization: Wernicke’s Area (posterior superior temporal gyrus)

(3) Anomic Aphasia – Fluent Aphasia (Left parieto-temporal junction region)

lesion of arcuate fasciculus so Brocca’s and Wernicke cannot communicate
Speech: multiple phases but few substantive words; rhythm and rate normal; few paraphasia,
Writing: penmanship and spelling preserved
Abnormal – R epetition and comprehension normal

Naming is markedly impaired
Localization: Wernicke’s Area; usually associated with lesions of the posterior inferior left temporal lobe but also may result from a variety of lesions that compromise visual, conceptual and language integration

Intrinsic Plasticity

central nervous system can reorganize after a lesion to compensate for lost function

studied using PET scan techniques to determine activity of certain regions of the brain

e.g.: with lesion in primary motor cortex, other regions of brain can assume function of lost tissue

bilateral cerebellum activation

ipsilateral primary motor cortex also Ý in importance and sends uncrossed fibers to control desired function