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Temporal lobe and limbic system

Temporal lobe and limbic system






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    Temporal lobe and limbic system Temporal lobe and limbic system Presentation Transcript

    •  The temporal lobe includes the superior, middle, and inferior temporal, lateral occipitotemporal, fusiform, lingual, parahippocampal, and hippocampal convolutions and the transverse gyri of Heschl Heschl gyri -constitute the primary auditory receptive area and are located within the sylvian fissure The cortical receptive zone for labyrinthine impulses is less well demarcated than the one for hearing but is probably situated on the inferior bank of the sylvian fissure, just posterior to the auditory area
    •  The superior part of the dominant temporal lobe is concerned with the acoustic or receptive aspects of language The middle and inferior convolutions are sites of visual discriminations; they receive fiber systems from the striate and parastriate visual cortices and, in turn, project to the contralateral visual association cortex, the prefrontal heteromodal cortex, the superior temporal cortex, and the limbic and paralimbic cortex Presumably these systems subserve such functions as spatial orientation, estimation of depth and distance, stereoscopic vision, and hue perception
    •  The most important functions of the hippocampus and other structures of the hippocampal formation (dentate gyrus, subiculum, entorhinal cortex, and parahippocampal gyrus) are in learning and memory There is an abundance of connections between the mediotemporal lobe and the entire limbic system
    •  Physiologically, two functional correlations stand out—that the temporal lobe is the great integrator of ―sensations, emotions, and behavior‖ (Williams) and that it is continuously active throughout life The temporal lobe seems to be the site where sensory modalities are integrated into ultimate self-awareness
    •  Disorders of special senses (visual, auditory, olfactory and gustatory) Time perception Language Memory Emotion and behaviour
    •  Superior homonymous quadrantanopia-not congruent Kluver bucy syndrome-bilateral lesions of temporal lobes Visual hallucinations of complex type including autoscopy-temporal lobe seizures
    •  Bilateral lesions of the transverse gyri of Heschl, while rare, are known to cause a central deafness Unilateral lesions of Heschl’s gyri were for a long time believed to have no effect on hearing; it has been found, however, that a number of subtle deficits can be detected with careful testing
    • Agnosia of soundsAmusiaAuditory verbal agnosia
    •  Agnosia for sounds-auditory sensations cannot be distinguished from one another Usually associated with word deafness or amusia Lesion involved right temporal lobe in isolated cases-Hecaen
    •  Amusia -the nondominant hemisphere is important for the recognition of harmony and melody (in the absence of words), but that the naming of musical scores and all the semantic (writing and reading) aspects of music require the integrity of the dominant temporal and probably the frontal lobes as well Word deafness-essential element of wernickes aphasia
    •  They may be elementary or complex In temporal lobe epilepsy, the auditory hallucinations are known to occur alone or in combination with visual or gustatory hallucinations, visual distortions, dizziness, and aphasia There may be hallucinations based on remembered experiences (experiential hallucinations)
    •  Elementary hallucinations and dreamy states have been reported with lesions of either temporal lobe, whereas the more complex auditory hallucinations and particularly polymodal ones (visual plus auditory) occur more often with left-sided lesions Complex but unformed auditory hallucinations (e.G., The sound of an orchestra tuning up), as well as entire strains of music and singing, occur with lesions that appear to be restricted to the pons (pontine auditory hallucinosis)
    •  In the superior and posterior part of the temporal lobe (posterior to the primary auditory cortex), there is an area that responds to vestibular stimulation by establishing one’s sense of verticality in relation to the environment The only clinical effect may be an illusion that the environment is tipped on its side or is upside down Epileptic activation of this area induces vertigo or a sense of disequilibrium
    •  In a temporal lobe seizure originating on either side, time may seem to stand still or to pass with great speed The most common disruptions of the sense of time occur as part of confusional states of any type The patient with a Korsakoff amnesic state is unable to place events in their proper time relationships, presumably because of failure of retentive memory, a function assignable to the medial temporal lobes
    •  Seizure foci in the medial part of the temporal lobe (in the region of the uncus) often evoke olfactory hallucinations This type of ―uncinate fit,‖ as originally pointed out by jackson and stewart, is often accompanied by a dreamy state, or, in the words of penfield, an ―intellectual aura‖ Hallucinations of taste are less common
    • I. Effects of unilateral disease of the dominant temporal lobe A. Homonymous upper quadrantanopia B. Wernicke’s aphasia (word-deafness—auditory verbal agnosia) C. Amusia (some types) D. Impairment in tests of verbal material presented through the auditory sense E. Dysnomia or amnesic aphasia F. Visual agnosia G. Occasionally amnesic (Korsakoff) syndromeII. Effects of unilateral disease of the nondominant temporal lobe A. Homonymous upper quadrantanopia B. Inability to judge spatial relationships in some cases C. Impairment in tests of visually presented nonverbal material D. Agnosia for sounds and some qualities of music contd.,
    • III. Effects of disease of either temporal lobe A. Auditory, visual, olfactory, and gustatory hallucinations B. Dreamy states with uncinate seizures C. Emotional and behavioral changes D. Delirium (usually nondominant) E. Disturbances of time perception IV. Effects of bilateral disease A. Korsakoff amnesic defect (hippocampal formations) B. Apathy and placidity c.Kluver-Bucy syndrome
    •  Emotion defined as any strong feeling state—e.g., fear, anger, excitement, love, or hate—associated with certain types of bodily changes (mainly visceral and under control of the autonomic nervous system) and leading usually to an impulse to action or to a certain type of behavior The components of emotion appear to consist of ◦ (1) the perception of a stimulus, which may be internal (an idea) or external, ◦ (2) the feeling, ◦ (3) the autonomic-visceral changes, ◦ (4) the outward display of affect, and ◦ (5) the impulse to a certain type of activity.
    • ―The hypothalamus, the anterior thalamic nucleus, the cingulate gyrus, the hippocampus and their interconnections, constitute a harmonious mechanism which may elaborate the functions of central emotion as well as participate in the emotional expression.‖ -James Papez, 1939  Broca, Papez, Kluver and Bucy  Parts of the brain underlying emotional behavior  Associated with the olfactory system; rhinencephalon = ―smell brain‖ http://www.hallym.ac.kr/~de1610/nana/chp-12n.htm#II
    • ANATOMY Identified medial surface of cerebrum that are different from the rest of cortex—called it border=limbic lobe Cortex surrounding corpus callosum Thought to be involved in olfaction
    •  Paul Broca (1824-1880): 1878: ―le grand lobe limbique‖ Refers to a ring of gray matter on the medial aspect of the cerebral hemispheres James Papez (1883-1958): 1930’s: defined a limbic system that might underlie the relationship between emotion and memory (Papez’ circuit).
    •  James Papez 1930s identified limbic structures involved in emotion (added the thalamic structures to the limbic lobe) Cingulate cortex to hippocampus to hypothalamus via the fornix and from hypothalamus to anterior nuclei of thalamus Neocortex connects to cingulate cortex Allows one to experience emotion
    • o Amygdaloid bodyo Hippocampus (―seahorse‖)o Cingulate gyuso Parahippocampal gyruso Hypothalamuso Mamillary bodieso Anterior nucleus of thalamus
    •  ―Emotional brain o Emotional and motivational aspects of behavior. o Provides emotional component to learning process: Especially the amygdala Associated with memory o Especially the hippocampus Associated with pain/pleasure, rage
    •  Greek name for almond shape Neurons at the pole of the temporal lobe below the cortex on the medial side Has 3 nuclei, basolateral, corticomedial and central Afferents from all lobes of neocortex & hippocampus and cingulate gyrus
    •  Basolateral ◦ Similar to cortex ◦ Projects to ventral striatum ◦ Has pyramidal like cells ◦ Receives input from primary sensory cortex, polysensory cortex and thalamus ◦ Connections are reciprocal Cortical ◦ Olfactory amygdala ◦ Receives direct input form olfactory system, both the olfactory bulb and olfactory cortex Central Medial group ◦ Main output of amygdaloid complex ◦ Input from hippocampus, orbitofrontal, insula, anterior cingulate cortex as well as basolateral group ◦ Projects to hypothalamus, brainstem via stria terminalis and amygdaloventral fugal pathway ◦ Part of ―central autonomic network‖
    •  Basolateral nuclei receive sensory input (visual, gustatory, auditory and tactile); also projects to cortex for perception of emotion Corticomedial nuclei receive olfactory inputs Central nuclei contain output neurons to hypothalamus and periaqueductal grey in brainstem for physiological responses
    •  Decreases emotional response Kluver-Bucy Syndrome=reduced emotionality Fearlessness Cannot recognize emotional expressions on faces that are fearful, anxious & angry but recognize happy & disgust Bilateral amygdala removal reduces memory
    •  Cause affective rage when basalateral nuclei is stimulated Corticomedial stimulation reduces aggression
    •  Require the amygdala and work through 2 pathways. Integrate information from all sensory systems and orchestrate the physiological and psychological response ◦ Ventral amygdofugal pathway ◦ Stria terminalis
    •  Androgen levels in males can alter aggressive behaviors Predatory aggression: purpose is getting food, little sympathetic NS activity ◦ Medial hypothalamus Affective aggresion: purpose is scare off enemies/protection ◦ Lateral hypothalamus
    •  Autonomic nuclei in the brainstem receive synaptic input from hypothalamus via ◦ Medial forebrain bundle ◦ Dorsal longitudinal fasciculus
    •  Depending on area, animal shows different behaviours Associated with eating, sniff & eat Associated with fear or anger Demonstrates 2 functions of hypothalamus ◦ Metabolic regulation; homeostasis ◦ Coordinated somatic & visceral responses
    •  Serotonin containing neurons located in Raphe nucleus in brainstem that project via medial forebrain bundle to hypothalamus & other limbic structures Aggressive mice have decreased serotonin turnover Drugs that block serotonin release or synthesis cause increase in aggression
    •  Greek: ―Sea Monster‖ Another terminology mess ◦ Allocortex/ archicortex ◦ Hippocampal formation (after Amaral and Witter)  Dentate gyrus  Hippocampus proper ―Cornu ammonis‖  Subicular complex  Subiculum  Presubiculum  parasubiculum  Entorhinal cortex
    •  Greek: ―Sea Monster‖ Another terminology mess ◦ Allocortex/ archicortex ◦ Hippocampal formation (after Amaral and Witter)  Dentate gyrus  Hippocampus proper ―Cornu ammonis‖  Subicular complex  Subiculum  Presubiculum  parasubiculum  Entorhinal cortex
    • •Afferents: •Much of cortex is reciprocally connected to entorhinal cortex •Cholinergic and GABA input via septal nuclei •Amygdala •VTA, LC, Raphe•Efferents •Via the fornix •Precommissural: septal nuclei •Post-commisural: mammillary bodies (to anterior thalamic nucleus via mammillothalamic tract)
    •  James Lange Theory 1884 Experience emotions IN RESPONSE to physiological changes in our body
    •  1927: Emotional experience can occur independently of emotion expression Transect animal spinal cord and emotional expression observed Removal or damage to somatic sensory system does not diminish emotion experience.
    •  I. Disturbances of emotionality due to: ◦ A. Perceptual abnormalities (illusions and hallucinations) ◦ B. Cognitive derangements (delusions) II. Disinhibition of emotional expression ◦ A. Emotional lability ◦ B. Pathologic laughing and crying III. Rage reactions and aggressivity IV. Apathy and placidity ◦ A. Kluver-Bucy syndrome ◦ B. Other syndromes (frontal and thalamic) V. Altered sexuality VI. Endogenous fear, anxiety, depression, and euphoria
    •  Delirium -Threatened by imaginary figures and voices that seem real The patient’s affect, emotional reaction, and visceral and somatic motor responses are altogether appropriate to the content of the hallucinations There also occurs a state of overwhelming emotionality in patients who are in severe acute pain
    •  Emotional lability is a sign of organic brain disease In this type of emotional disturbance, the response, while excessive, does not reach the degree of forced emotionality of the special form of lability described as pseudobulbar furthermore, it is appropriate to the stimulus and the affect is congruent with the visceral and motor components of the expression.
    •  This form of disordered emotional expression, characterized by outbursts of involuntary, uncontrollable, and stereotyped laughing or crying The term emotional incontinence applied by psychiatrists Forced laughing and crying always has a pathologic basis in the brain, either diffuse or focal
    •  Bilateral strokes (lacunes in the cerebral hemispheres or pons most often, and after several strokes in succession) Binswanger diffuse leukoencephalopathy Amyotrophic lateral scerlosis with pseudobulbar palsy Progressive supranuclear palsy Multiple sclerosis with bilateral corticobulbar demyelinative lesions Bilateral traumatic lesions of the hemispheres Hypoxic-ischemic encephalopathy Pontine myelinolysis Wilson disease
    •  In this state there is often a striking incongruity between the loss of voluntary movements of muscles innervated by the motor nuclei of the lower pons and medulla and the preservation of movement of the same muscles in yawning, coughing, throat clearing, and spasmodic laughing or crying (i.e., in reflexive pontomedullary activities)
    •  In such cases, on the slightest provocation and sometimes for no apparent reason, the patient is thrown into a stereotyped spasm of laughter that may last for many minutes, to the point of exhaustion But more often, the opposite happens—the mere mention of the patient’s family or the sight of the doctor provokes an uncontrollable spasm of crying
    •  The severity of the emotional incontinence or the ease with which it is provoked does not always correspond with the severity of the pseudobulbar paralysis or with an exaggeration of the facial and masseter (―jaw jerk‖) tendon reflexes
    •  Descending motor pathways which naturally inhibit the expression of the emotions were interrupted- Wilson Supranuclear pathways are involved somewhere in the brainstem between thalamus and medulla and lesions are bilateral in practically all instances- Poeck
    •  Rage reactions of may be encountered in the following medical settings 1.Temporal lobe seizures 2.Sociopaths 3.Acute or Chronic neurological disorders 4.Metabolic or toxic encephalopathies
    •  Temporal lobe seizures-a directed attack of uncontrollable rage may occur either as part of a seizure or as an interictal phenomenon -Gastaut Lesser degrees of aggressive behaviour are more common-brief in duration and poorly directed
    •  Acute neurological disorders-Hemorrhagic leukoencephalitis, lobar hemorrhage, infarction, and herpes simplex encephalitis affecting the medio-orbital portions of the frontal lobes and anterior portions of the temporal lobes may cause rage reactions Outbursts of Rage can be seen with temporal lobe gliomas
    • KLUVER-BUCY SYNDROME In 1939, Kluver and Bucy described a behaviouralsyndrome in rhesus monkeys that followedbilateral temporal lobectomyManifestations – 1.Hypersexuality 2.Excessive oral tendencies 3.Loss of normal fear and anger 4.Hypermetamorphosis 5.Psychic blindness 6.Dietary changes
    •  In 1955 Terzian first reported the same syndrome in humans after bilateral temporal lobectomy Causes- 1.Herpes encephalitis 2.Picks disease 3.Alzheimer disease 4.Cerebrovascular accidents 5.Cerebral trauma 6.temporal lobe epilepsy The common feature of all etiologies was bilateral mesial temporal lobe destruction or dysfunction
    •  Hypersexuality –indiscriminate sexual behaviour-seen with orbitofrontal lesions and loss of sexual drive seen with superior frontal lesions In rare cases, extreme hypersexuality marks the onset of encephalitis or develops gradually with tumors of the temporal region. Possibly the limbic parts of the brain are disinhibited, the ones from which MacLean and Ploog could evoke penile erection and orgasm by electrical stimulation (medial dorsal thalamus, medial forebrain bundle, and septal preoptic region). In clinical practice, the commonest cause of disinhibited sexual behavior, next to the aftermaths of head injury and cerebral hemorrhage, is the use of dopaminergic drugs in Parkinson disease.
    •  Hyposexuality -most often due to a depressive illness Drugs -antihypertensive, anticonvulsant, serotoninergic antidepressant, and neuroleptic drugs Sexual arousal as an ictal phenomenon is apt to occur in relation to temporal lobe seizures, particularly when the discharging focus is in the mediotemporal region
    •  Depression is less frequent as an ictal emotion, although it occurs often enough as an interictal phenomenon (Benson et al) Odd mixtures of depression and anxiety are often associated with temporal lobe tumors and less often with tumors of the hypothalamus and third ventricle Elation and euphoria are less well documented as limbic phenomena
    •  The phenomenon of acute fear and anxiety occurring as a prelude to or part of a seizure neuronal circuits subserving fear are coextensive with those of anger; both are thought to lie in the medial part of the temporal lobe and amygdala Destruction of the central part of the amygdaloid nuclear complex abolishes fear reactions. These nuclei are connected to the lateral hypothalamus and midbrain tegmentum
    • Thank you