– language processing, motor control, visual and somatosensory appreciation of the opposite side of the body
Broca’s Aphasia Þ inferior posterior frontal gyrus; difficulty in initiating and producing speech and writing with relative preservation of understanding of speech and writing (See later)
Wernicke’s Aphasia Þ posterior superior temporal gyrus; poor comprehension of written and spoken language, and verbal and written output that makes little sense; contains neologisms – words that do not exist and paraphrasic errors – use of wrong words or wrong syllables within a word
Lesions
:
(1) Language disorders
: Broca’s aphasia, Wernicke’s aphasia, and acquired reading disorders from lesions disrupting communication between visual cortex and the language centers;
(2) Visual field defects
: inferior quadrantantopsia Þ lesion in parietal lobe or superior portion of calcarine cortex in occipital lobe; superior quadrantantopsia Þ lesion in temporal lobe or inferior portion of calcarine cortex; unilateral loss of optokinetic nystagmus Þ lesion at junction of parietal and occipital cortex
(3) Epilepsy
: focal sensory and motor seizures Þ ictal focus is in region of cortex that when stimulated would produce the ictal phenomenon; exception Þ ictal focus quickly excites a second area of cortex and which is responsible for ictal activity
(4) Neglect of right side of body or environment
(parietal lobe)
(3) Right
– motor and sensory signs are similar to that of left hemisphere except that the left side of the body is involved
language function usually spared with lesions of the non-dominant right hemisphere; naming may be compromised
spatial perception may be disrupted
Frontal Lobe Damage
Motor Findings: Primary Motor Cortex
Þ contralateral spastic paresis
premotor and Supplementary Motor Cortex
Þ actions slow and innacurate; strength may be normal;
apraxia: impaired ability to carry out complex/multistep motor actions
frontal eye fields (brodmann 8)
Þ inability to voluntary direct gaze to opposite side (voluntary nystagmus); lesion Þ gaze to same side; epilepsy Þ gaze to opposite side
Anosmia: loss of sense of smell
Þ damage to orbital frontal cortex or to olfactory groove
Behavioral Changes: (most prominent with bilateral lesions)
Orbital Frontal Cortex
Þ social withdrawal; indifference to surroundings, incontinence
Orbital Cortex and Medial Frontal Cortex
Þ findings of orbital frontal cortex plus lack of spontaneity and brief spoken responses (abulia)
Frontal Convexity: loss of social inhibition, impulsiveness, loss of social concern (lesion = Pick’s disease)
Entire Prefrontal Cortex sparing Orbital and Medial Frontal Cortex: loss of initiative and concern, severe short term memory loss, confabulation
Þ together these findings are called Korsakoff’s Syndrome (psychosis)
Thalamus
Medal Doral Nucleus (MDN)
Þ projects to prefrontal cortex
Karsokoff’s Psychosis
Þ due to damage of the MDN from chronic alcohol abuse: an amnestic syndrome characterized by confusion and severe impairment of memory, especially for recent events, for which the patient compensates by confabulation; frontal lobe is not myelinated until the age of 6 and the behavior of children is similar to that of a patient with Korsakoff’s Syndrome
Parietal Lobe
– processes sensory information and combines somatic sensory information with visual information
Either Side
: contralateral sensory loss
primary sensory cortex – primary modalities
associated sensory cortices – integrated modalities (graphesthesia – inability to recognize symbols written on skin, astereognosis – inability to recognize objects or forms by touch, two point discrimination impaired)
contralateral inferior quadrananopia
Right Parietal Hemisphere
impaired spatial perception (self and external)
inattention to the "left world" and "left body" (neglect)
anosognosia
Þ denial of deficit
dressing apraxia
Left Parietal Hemisphere
impaired right-left discrimination
agraphia
Þ loss of the ability to manipulate a pen or other writing object; dyslexia – inability to recognize letters or words correctly; dysgraphia: inability to write without paralysis; dyscalculia: impaired math ability; dynomia: difficulty finding words for written or oral expression