Temporal lobe Dr.Pradnya Kasar Dept. of Psychiatry GGMC 7th July, 2020 Introduction • • • • • • • Anatomy of temporal lobe Blood supply of temporal lobe Connections of temporal cortex Functions of temporal lobe Temporal lobe lesions Temporal lobe testing Temporal lobe epilepsy Anatomy of temporal lobe Lateral view 1. The temporal lobe occupies the area inferior to the lateral sulcus and anterior to occipital cortex. The lateral surface of the temporal lobe is divided into three gyri by two sulci 2. The superior and middle temporal sulci run parallel to the posterior ramus of the lateral sulcus and divide the temporal lobe into the superior, middle, and lnferior temporal gyri 3. The inferior temporal gyrus is continued onto the inferior surface of the hemisphere 4.Heschl’s gyrus ( aka Transverse temporal gyrus) Image A)The three major gyri visible on the lateral surface of the temporal lobe. Broadmann’s areas The temporal regions on the lateral surface are divided into 1. Auditory regions(Brodmann’s areas 41, 42, and 22 ) 2.Ventral visual stream on the lateral temporal lobe(areas 20, 21, 37, and 38 ). 3.The visual regions are often referred to as inferotemporal cortex or by von Economo’s designation, TE. B)Broadman’s cytoarchitectonic zones on the lateral surface. Areas 20,21 and 38 are often referred to by von Bonin and Bailey’sdesignation TE. Anatomy of temporal lobe Medial view Subcortical temporal-lobe structures include the limbic cortex, the amygdala, and the hippocampal formation . The medial temporal region (limbic cortex) includes the amygdala and adjacent cortex (uncus), the hippocampus and surrounding cortex (subiculum, entorhinal cortex, perirhinal cortex), and the fusiform gyrus. Image C) The gyri visible on a medial view of the temporal lobe. The uncus refers to the anterior extension of the hippocampal formation. The parahippocampal gyrus includes areas TF and TH. D) TH and TF at the posterior end of the temporal lobe (parahippocampal cortex ) Temporal lobe 1.The primary auditory area (Brodmann areas 41 and 42) includes the gyrus of Heschl and is situated in the Inferior wall of the lateral sulcus 2.Projection fibers to the auditory area arise principally in the medial geniculate body and form the auditory radiation of the internal capsule. 3.The anterior part of the primary auditory area is concerned with the reception of sounds of low frequency, and the posterior part of the area is concerned with the sounds of high frequency. A unilateral lesion of the auditory area produces partial deafness in both ears, the greater loss being in the contralateral ear. This can be explained on the basis that the medial geniculate body receives fibers mainly from the organ of Corti of the opposite side as well as some fibers from the same side. 4.The secondary auditory area (auditory association cortex) is situated posterior to the primary auditory area in the lateral sulcus and in the superior temporal gyrus (Brodmann area 22). It receives impulses from the primary auditory area and from the thalamus 5.The secondary auditory area is thought to be necessary for the interpretation of sounds and for the association of the auditory input with other sensory information. 6.The sensory speech area of Wernicke is localized in the left dominant hemisphere, mainly in the superior temporal gyrus, with extensions around the posterior end of the lateral sulcus into the parietal region. The Wernicke area is connected to the Broca area by a bundle of nerve fibers called the arcuate fasclculus 7.The Wernicke area permits understanding of written and spoken language and enables a person to read a sentence, understand it, and say it out loud Heschl’s gyri 1.The transverse temporal gyri (Heschl's gyri or Heschl's convolutions) 2.Found in the area of primary auditory cortex buried within the lateral sulcus of the human brain, occupying Brodmann areas 41 and 42. 3.It is the first cortical structure to process incoming auditory information. Insula The sulci of the temporal lobe contain a lot of cortex, as can be seen in Figure . In particular, the Sylvian fissure contains tissue forming the insula, which includes the gustatory cortex as well as the auditory association cortex. Image - Internal structure of the temporal lobe. (Top) Lateral view of the left hemisphere illustrating the relative positions of the amygdala and hippocampus buried deep in the temporal lobe. The vertical lines indicate the approximate location of the sections in the bottom illustration. (Bottom) Frontal sections through the left hemisphere illustrating the cortical and subcortical regions of the temporal lobe. Blood supply Connections of temporal cortex The temporal lobes are rich in internal connectionsAfferent projections from the sensory systems Efferent projections to the parietal and frontal association regions, limbic system, and basal ganglia The neocortex of the left and right temporal lobes is connected by the corpus callosum, whereas The neocortex of the medial temporal cortex and amygdala are connected by the anterior commissure. The connections are as follows1.Ventral hierarchical Sensory Pathway 2.Dorsal auditory pathway 3. Polymodal pathway (Visual and auditory projections to polymodal temporal regions) 4.Medial temporal projections 5. Frontal lobe projections A hierarchical sensory pathway The hierarchical progression of connection emanate from the primary and secondary auditory and visual areas, ending in the temporal pole. Auditory and visual protections run parallel to each other. (F:stimulus recognition) Image A- Auditory and visual information progress ventrally from the primary regions toward the temporal pole, en route to the medial temporal regions. A dorsal auditory pathway Traveling from the auditory areas to the posterior parietal cortex, concerned with directing movements with respect to auditory information. (F:spatial location of auditory input) Image -Auditory information also forms a dorsal pathway to the posterior parietal cortex. A polymodal pathway This pathway is a series of parallel projections from the visual and auditory association areas into the polymodal regions of the superior temporal sulcus (F:stimulus categorization) Image -(B) Auditory, visual, and somatic outputs go to the multimodal regions of the superior temporal sulcus. STS- superior temporal sulcus A medial temporal projections The projection from the auditory and visual association areas into the medial temporal or limbic regions goes first to the perirhinal cortex, then to the entorhinal cortex, and finally into the hippocampal formation or the amygdala or both The hippocampal projection is a major one, forming the perforant pathway. (F: long term memory) Image(C) Auditory and visual information goes to the medial temporal region, including the amygdala and the hippocampal formation. A frontal lobe projections This series of parallel projections reaches from the association areas to the frontal lobe (F:various aspects of movement control, short-term memory and affect) Image(D) Auditory and visual information goes to two prefrontal regions, one on the dorsolateral surface and the other in the orbital region (area 13). Functions of temporal lobe 1.Visual memory 2.Memory formation (long term storage of sensory inputs) 3.Processing sensory input -Auditory (superior temporal gyrus)- processing input -Visual (fusiform and inferior temporal gyrus)- object recognition -Olfactory (entorhinal cortex) -Gustatory (insular cortex) -Language recognition (Wernicke's area) -Identification and Categorization of Stimuli -Emotional response is associated with a particular stimulus Functional zones Four functional zones 1. Auditory processes (superior temporal gyrus) 2. Visual processes (inferior temporal cortex) 3. Integration of these processes for emotion (amygdala) 4.Spatial navigation and spatial and object memory (hippocampus and associated cortex) Auditory and visual functions The brain's temporal lobe combines auditory and visual information. 1. The superior and medial aspect of the temporal lobe receives auditory input from the part of the thalamus that relays information from the ears. 2. The inferior part of the temporal lobe does visual processing for object and pattern recognition. 3.The medial and anterior parts of the temporal lobe are involved in very high-order visual recognition (being able to recognize faces), as well as recognition depending on memory. Amygdala Location: Part of Limbic System, at the end of the hippocampus Function: Responsible for the response and memory of emotions, especially fear The amygdala is the reason we are afraid of things outside our control. It also controls the way we react to certain stimuli, or an event that causes an emotion, that we see as potentially threatening or dangerous. Numerous studies have been performed where researches have used deep lesioning to remove the amygdala of rats. After this procedure, the rats were said to have no fear of anything. The removal of the amygdala had taken away the rats' memory of fear, therefore the rats did not fear anything! Organisation and categorisation The temporal lobe adds two features to both auditory and visual information— tone (affect) and categorization. The ability to organize material is especially important for language and memory. For example, categorizing makes it possible to comprehend complex, extended sentences, including both the meaning of individual clauses and the information inferred from them For eg when Asked to learn a list of words such as “dog, car, bus, apple, rat, lemon, cat, truck, orange,” most of us will organize the words into three different cate- gories—animals, vehicles, and fruit. If the list is later recalled, the items are likely to be recalled by category, and recall of the categories is likely to be used as an aid in recall of the items Hippocampus When you changed routes and went elsewhere, you used the hippocampus. The hippocampus contains cells that code places in space; together, these cells allow us to navigate space and to remember where we are ( memories for object location). Whereas the parietal lobe processes spatial location with respect to movement. Location: Part of the Limbic system, in each temporal lobe Function: 1.Responsible for processing of long term memory 2.Emotional responses 3.Responsible for the memory of the location of objects or people Alzheimer's disease has been proven to have affected and damaged this area of the brain. Temporal lobe Lesions Disorders of auditory perception Cortical deafness - Bilateral damage to the primary auditory cortex will produce cortical deafness, an absence of neural activity in the auditory regions. Auditory hallucinations, which result from spontaneous activity in the auditory regions, are essentially the opposite of cortical deafness. Auditory hallucination is the perception of sounds (hearing voices) that are not actually present . Auditory Hallucinations • • The adjoining snapshot illustrates that the verbal hallucinations activated the primary auditory cortex , Broca’s area and the speech zone in the posterior temporal cortex. These results suggests that hallucinations have their origin in the patient’s own inner language systems,, which leads to perception that voices are coming from an external source.The limbic activity presumably results from the anxiety generated by hearing voices, especially hostile voices. Disorders of music perception Zatorre suggested that the right temporal lobe has a special function in extracting pitch from sound, regardless of whether the sound is speech or music. In regard to speech, the pitch will contribute to “tone” of voice, which is known as prosody. The perception of timbre, is impaired by right temporal lesions. (Timbre refers to the distinctive character of a sound, the quality by which it can be distinguished from all other sounds of similar pitch and loudness. ) Zatorre emphasized the key difference: The left hemisphere is concerned more with speed and the right hemisphere with distinguishing frequency differences, a process called spectral sensitivity. Disorders of visual perception Milner, who found that her patients with right temporal lobectomies were impaired in the interpretation of cartoon drawings( non-verbal) in the McGill Picture-Anomalies Test Imgae-Tests for visual disorders. (A) Meier and French’s test, in which the subject must identify the drawing that is different. (B) Sample of the Gottschaldt Hidden-Figures Test, in which the task is to detect and trace the sample (upper drawing) in each of the figures below it. (C) Rey Complex-Figure Test, in which the subject is asked to copy the drawing as exactly as possible. (D) Sample of the Mooney Closure Test, in which the task is to identify the face within the ambiguous shadows. • Temporal lobe lesions Temporal lobe lesions • Left superior temporal gyrus • Right superior temporal gyrus • Inferior temporal gyrus • Fusiform gyrus difficulty in discriminating speech inability to discriminate melodies and produce prosody inability to recognize objects, called Visual agnosia inability to recognize face, called Prosopagnosia (face blindness) Damage to the visual regions of the temporal lobe disrupt the recognition of complex visual stimuli, such as faces. Damage to medial temporal regions produces deficits in affect, personality, spatial navigation, and object memory. Wernicke’s aphasia The Wernicke area permits understanding of written and spoken language and enables a person to read a sentence, understand it, and say it out loud Wernicke’s aphasia 1.Loss of ability to understand the spoken and written word, that is , Receptive/ sensory aphasia . 2.Speech is unimpaired, and the patient can produce fluent speech(Since the Broca area is unaffected,). 3.The patient is unaware of the meaning of the words he or she uses and uses Incorrect words or even nonexistent words. The patient is also unaware of any mistakes. Temporal lobe lesions Organization & Categorization • Left temporal lobe lobotomies lead to impairment in the ability to categorize words or pictures of objects • Posterior lesions lead to a difficulty in recognizing specific word categories Language Comprehension • Stimuli can be interpreted in different ways depending on the context Example: Fall - the season or a tumble Memory • Antero-grade Amnesia. — Amnesia for events after bilateral removal of the medial temporal lobes including amygdala and hippocampus • Inferior -temporal Cortex. - Conscious recall of information • Left temporal lobe. - Verbal memory • Right temporal lobe. -Impaired recall of nonverbal material Clinical neuropsychological assessment Of temporal lobe damage Wechsler Memory Scale Wechsler Memory Scale and was asked to repeat it as exactly as possible. “Anna Thompson of South Boston, employed as a scrub woman in an office building, was held up on State Street the night before and robbed of $15. She had four little children, the rent was due and they had not eaten for two days. The officers, touched by the woman’s story, made up a purse for her.” If Mr.A has difficulty in recalling the paragraph above but his immediate recall of digits was good; he could repeat strings of seven digits accurately. Similarly, his recall of geometric designs was within normal limits, illustrating the asymmetry of memory functions, because his right temporal lobe was intact. Similarly , if Mr. B performed within normal limits on formal tests of verbal memory, such as the story of Anna Thompson, but was seriously impaired on formal tests of visual memory, especially geometric drawings , is suggestive of right temporal lobe lesion. Temporal lobe epilepsy 1. Temporal lobe epilepsy (TLE) was defined in 1985 by the International League Against Epilepsy (ILAE) as a condition characterized by recurrent unprovoked seizures originating from the medial (Hippocampus, Para-hippocampal gyrus, Amygdala) or lateral temporal lobe (Neocortex) 2. Begins in late childhood or early adulthood 3. Most common of anatomically defined syndromes (around 60%) 4. Most varied and complex auras 5. Resembles with symptoms of psychiatric disorder Compared to idiopathic schizophrenia - less flattening of affect - increase in obsessional traits - absence of family history of psychosis - Lishman’s Organic Psychiatry Causes 1. Hippocampus sclerosis a.k.a. Mesial temporal sclerosis or Ammon’s horn sclerosis 2. Childhood febrile convulsions 3. Scars 4. Infarcts 5. Dysembryoplastic neuroepithelial tumours 6. Cavernous angiomas 7. Gliomas 8. Cortical dysplasia 9. Gliosis secondary to encephalitis or meningitis - Lishman’s Organic Psychiatry Mesial temporal sclerosis Hippocampal sclerosis or Ammon’s horn sclerosis Strongly associated with h/o childhood febrile convulsions Types - Simple partial seizures - Complex partial seizures Temporal lobe seizures characteristically have - Gradual onset -Conspicuous motionless stare -Relatively prolonged -With automatisms often for 2 mins or more -Wide variety of auras Clinical presentation of TLE Temporal-lobe epilepsy has traditionally been associated with personality characteristics that overemphasize trivia and the petty details of daily life. Clinical features include1. Pedantic speech ( overly formal speaking style that is inappropriate to the conversational settings ) 2.egocentricity 3. Perseveration in discussions of personal problems (sometimes referred to as “stickiness,” because one is stuck talking to the person) 4. Paranoia, 5.Preoccupation with religion, 6.Proneness to aggressive outbursts. This constellation of behaviors produces what is described as temporal-lobe personality, Aura 1.Aura’s are described as having autonomic features and visceral sensations a.Epigastric aura most common ( reported up to 50% of patients with TLE (Henkel et al. 2002) Consists of ill-defined sensations rising from the epigastrium towards throat , described as churning, ‘butterflies’ or feeling of nervousness b. Cephalic aura - odd sensation in head c.Others Changes in skin colour, blood pressure, heart rate perspiration, salivation , piloerection, etc. 2.Affective aura -Affective experiences – in ¼ th of cases -Intrinsic part of seizure & not reaction to a aura -Anxiety (ICTAL FEAR )- most common -Others- depression, guilt and anger, joy, elation 3.There is a often characteristic ‘march’ Ex: from initial epigastric sensation to gustatory hallucinations to forced thinking , or From intense deja vu to an overwhelming sense of fear. Lateralising values of temporal foci • Versive ( unquestionably, forced and involuntary , resulting in sustained unnatural positioning) Gastaut -Geschwind syndrome Characteristic personality syndrome consisting of 1. Circumstantiality, 2. Hypergraphia (Behavioural condition characterised by intense desire to write or draw) 3. Altered sexuality (usually hyposexuality, meaning a decreased interest), and 4. Intensified mental life (deepened cognitive and emotional responses), hyper-religiosity and/or hyper-morality or moral ideas that is present in some epilepsy patients. This syndrome is particularly associated with temporal lobe epilepsy occurring in the left hemisphere . Kluver- Bucy syndrome Bilateral lesions of the anterior temporal lobe (including amygdaloid nucleus). 1. Amnesia- Inability to recall memories. Its nature is both anterograde and retrograde, meaning new memories cannot be formed and old memories cannot be recalled. 2.Docility. Exhibiting diminished fear responses or reacting with unusually low aggression. -Also been termed "placidity" or “tameness”. 3.Dietary changes and/or Hyperphagia - Eating inappropriate objects (pica) and/or overeating. 4.Hyperorality. "an oral tendency, or compulsion to examine objects by mouth". 5. Hypersexuality Heightened sex drive or a tendency to seek sexual stimulation from unusual or inappropriate objects. 6. Visual agnosia. Inability to recognize familiar objects or people. Inconsistent criteria include: 7.Hypermetamorphosis “An irresistible impulse to notice and react to everything within sight”. 8. Lack of emotional response, diminished emotional affect. 9.Memory loss. • • • • References - Ryan splittgerber- Snells clinical neuroanatomy -8th ed Lishman organic psychiatry -4th ed Kolb & Whishaw , chap 15- psychology and Neuroscience.
