TEMPORAL LOBES AND LIMBIC SYSTEM

ANATOMY

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

ANATOMY

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

CLINICAL EFFECTS

Superior homonymous quadrantanopia-not congruent

Kluver bucy syndrome-bilateral lesions of temporal lobes

Visual hallucinations of complex type including autoscopy-temporal lobe seizures

VISUAL DISORDERS

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

AUDITORY DISORDERS

Agnosia of sounds

Amusia

Auditory verbal agnosia

AUDITORY AGNOSIAS

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)

AUDITORY 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

VESTIBULAR DISTURBANCES

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

DISTURBANCES OF TIME PERCEPTION

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

DISTURBANCES OF SMELL AND TASTE

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) syndrome

II. 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.,

SUMMARY OF TEMPORAL LOBE SYNDROMES

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

LIMBIC LOBES AND NEUROLOGY OF EMOTION

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 LIMBIC SYSTEM

Broca, Papez, Kluver and Bucy

Parts of the brain underlying emotional behavior

Associated with the olfactory system; rhinencephalon = “smell brain”

“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

http://www.hallym.ac.kr/~de1610/nana/chp-12n.htm#II

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

Limbic Lobe 1878 Paul Broca

ANATOMY

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).

History

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

PAPEZ CIRCUIT

o Amygdaloid bodyo Hippocampus (“seahorse”)o Cingulate gyuso Parahippocampal gyruso Hypothalamuso Mamillary bodieso Anterior nucleus of thalamus

COMPONENTS

“Emotional brainoEmotional and motivational aspects of behavior.oProvides emotional component to learning

process: Especially the amygdala

Associated with memoryoEspecially the hippocampus

Associated with pain/pleasure, rage

FUNCTIONS

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

AMYGDALA

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”

One view(based on Heimer, 1996)

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

INPUT TO AMYGDALA

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

DAMAGE TO AMYGDALA

Cause affective rage when basalateral nuclei is stimulated

Corticomedial stimulation reduces aggression

ELECTRICAL STIMULATION OF AMYGDALA

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

LEARNED BEHAVIORS

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

AGGRESSIVE BEHAVIORS

Do Not learnPathway Names

Autonomic nuclei in the brainstem receive synaptic input from hypothalamus via

◦ Medial forebrain bundle◦ Dorsal longitudinal fasciculus

HYPOTHALAMUS-BRAINSTEM

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

ELECTRICAL STIMULATION OF HYPOTHALAMUS

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

SEROTONIN

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

The Hippocampus

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

The Hippocampus

Connections•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

Theories of Emotion

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.

Cannon-Bard Theory

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

NEUROLOGY OF EMOTIONAL DISTURBANCES

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

DISTURBANCES OF EMOTIONALITY

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.

EMOTIONAL LABILITY

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

PATHOLOGIC LAUGHING AND CRYING

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

CAUSES OF PSEUDOBULBAR AFFECTIVE DISPLAY

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

MECHANISM

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

AGRESSION,ANGER,RAGE

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 behavioural

syndrome in rhesus monkeys that followed bilateral temporal lobectomy

Manifestations – 1.Hypersexuality 2.Excessive oral tendencies 3.Loss of normal fear and anger 4.Hypermetamorphosis 5.Psychic blindness 6.Dietary changes

APATHY AND PLACIDITY

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.

ALTERED SEXUALITY

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

ACUTE FEAR,ANXIETY,ELATION AND EUPHORIA

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