Chapter 15: The Temporal Lobes and Networks PDF

4/16/24 1 Chapter 15 The Temporal Lobes and Networks 2 Learning Objectives Describe the anatomy of the temporal lobe Explain the functions of the temporal lobe Identify the networks of the temporal lobe Characterize the symptoms of lesions of the temporal lobe Explain how neuropsychologists assess t...

4/16/24 1 Chapter 15 The Temporal Lobes and Networks 2 Learning Objectives Describe the anatomy of the temporal lobe Explain the functions of the temporal lobe Identify the networks of the temporal lobe Characterize the symptoms of lesions of the temporal lobe Explain how neuropsychologists assess temporal-lobe damage 3 Portrait: Living With Temporal Lobe Damage H.H. –40 years old, successful lawyer –Left wife of 15 years to join a fringe religious group –Experienced a seizure and a left temporal lobe tumor was found –Tumor removed and H.H. was able to return to his job –Left with word-finding difficulties and religiousness 4 Temporal-Lobe Anatomy Temporal lobe includes the neocortex, limbic cortex, and olfactory cortex Tissue below the Sylvain Fissure and anterior to the occipital cortex Subcortical structures of the temporal lobe include the amygdala and hippocampus Temporal lobe is connected to other regions throughout the brain 5 Internal Structure of the Temporal Lobe 6 Subdivisions of the Temporal Cortex There are several different systems for identifying subdivisions of the temporal lobe, and more subdivisions have been identified by recent studies Rough subdivisions of the lateral surface include auditory areas and areas associated with the ventral visual stream (AKA inferotemporal cortex) Olfactory (pyriform) cortex is found on the medial surface 1 inferotemporal cortex) Olfactory (pyriform) cortex is found on the medial surface The pyriform cortex continues rostrally into the frontal lobe as well. Deep sulci increase the surface area of the temporal lobe Insula, deep within the Sylvian (lateral) fissure, includes the gustatory cortex, auditory association cortex Superior temporal sulcus contains multimodal association areas Receives input from auditory, visual, and somatic regions 7 The temporal sulci enfold a lot of cortex In particular, the lateral (Sylvian) fissure contains tissue forming the insula, which includes the gustatory cortex as well as the auditory association cortex. The superior temporal sulcus (STS) separates the superior and middle temporal gyri and houses a significant amount of neocortex The superior temporal sulcus (STS) separates the superior and middle temporal gyri and houses a significant amount of neocortex Superior temporal sulcus contains multimodal association areas 8 Cortical areas TH and TF, at the posterior end of the temporal lobe are often referred to as the parahippocampal cortex. The fusiform gyrus and inferior temporal gyrus are functionally part of the lateral temporal cortex the cortical region lying along the boundary of the temporal and parietal lobes is often called the temporal–parietal junction (TPJ). The TPJ is consistently shown to be active in neuroimaging studies investigating attention, memory, language, and social processing. the TPJ is proposed as being central to decision making in a social context 9 10 Cytoarchitecture of the Temporal Lobe Connections of the Temporal Cortex Rich in internal connections Afferent Projections from sensory systems 9 10 Rich in internal connections Afferent Projections from sensory systems Efferent Projections to the parietal and frontal association regions, limbic system, and basal ganglia Left and Right Connected Via: – Corpus Callosum Medial temporal cortex and amygdala via: –Anterior Commissure Six Distinct Connections 11 Connections of the Temporal Lobe 1. Hierarchical Sensory Pathway sub-serves stimulus recognition –Incoming Auditory and Visual Information –Stimulus Recognition –Hierarchical progression of connections from primary and secondary auditory and visual areas, ending in the temporal pole. –Parallel Ventral visual and auditory streams 12 Connections of the Temporal Lobe 2. Dorsal Auditory Pathway is concerned with directing movements with respect to auditory information –From Auditory cortex to Posterior Parietal –Detection of spatial location/movement –Analogous to visual dorsal stream 13 Connections of the Temporal Lobe 3. Polymodal Pathway probably underlies stimulus categorization Series of parallel projections from Auditory and Visual association Areas into the Polymodal regions of STS Stimulus Categorization 14 Connections of the Temporal Lobe 4. Medial Temporal Projection crucial to long-term memory From Auditory and Visual association Areas to the medial temporal lobe, limbic cortex, goes first to the PrC, then to the ERC and finally to hippocampal formation or the amygdala or 14 temporal lobe, limbic cortex, goes first to the PrC, then to the ERC and finally to hippocampal formation or the amygdala or both A pathway that connects (“perforates”) the hippocampus to medial temporal (limbic) regions; when disrupted, results in major hippocampal dysfunction. Long-term Memory 15 Connections of the Temporal Lobe 5. Frontal Lobe Projection necessary for various aspects of movement control, short-term memory, and affect Auditory and Visual association Cortex to two separate areas in Frontal Lobe Movement Control Short-term Memory Affect 16 6. Olfactory Olfactory projections are related to odor perception and memory. Connections run from the olfactory bulb to the temporal pyriform cortex which has connections with the entorhinal and perirhinal cortical areas involved in memory 17 Anatomy of the Ventral Stream Ventral stream was initially understood as a hierarchical visual pathway from occipital to temporal pole, but newer research suggests there are at least six distinct cortical and subcortical pathways comprising the ventral stream Projections from occipitotemporal pathway project to striatum to support skill learning Pathway from inferotemporal cortex to amygdala supports the processing of emotional stimuli Pathway from inferotemporal cortex to ventral striatum provides information about stimulus valence Multiple pathways from area TE project to the medial temporal lobe, orbitofrontal cortex, and ventrolateral prefrontal cortex; are involved in long-term memory, object–reward pairings, and 18 lobe, orbitofrontal cortex, and ventrolateral prefrontal cortex; are involved in long-term memory, object–reward pairings, and working memory 18 1. Occipitotemporal-Neostriatial Network In the first pathway, a set of subcortical projections from every region of the occipitotemporal pathway (from Figure 15.5A) extends to the neostriatum, comprising the caudate nucleus plus putamen of the basal ganglia. These projections form the occipitotemporal–neostriatial network diagrammed at the top of Figure 15.5B. This network functions to support types of habit and skill learning dependent on vision 19 Second pathway from TE, amygdala-bound projections from inferotemporal regions allow processing of emotionally salient stimuli. Third pathway travels from inferotemporal cortex to the ventral striatum (nucleus accumbens, another basal ganglia component) to support the assignment of stimulus valence (potency). 20 The three remaining pathways from TE project to other cortical regions. The medial temporal pathway: long-term memory Orbitofrontal pathway: object-reward association Ventrolateral prefrontal pathway: object working memory. 21 Ventral Stream Expanded 22 Theory of Temporal-Lobe Function Temporal lobe houses the primary auditory cortex, secondary auditory and visual cortex, limbic cortex, part of the primary olfactory cortex, and the amygdala and hippocampus. Temporal lobe analyzes sensory information as it enters the nervous system- 4 basic sensory functions Processes auditory input Recognizes visual objects 23 Processes auditory input Recognizes visual objects Stores long-term memories Processes olfactory input 23 1. Sensory Processes Quickly categorizing objects is important for accurate perception and memory Need to shift attention from one feature to another, depending on what is most relevant Damage to temporal lobe results in deficits in identifying and categorizing stimuli There is no difficulty in locating the stimulus or recognizing that it is present, (P. partial and primary sensory, respectively) Cross-modal matching enables the integration of visual and auditory information and likely involves the superior temporal sulcus The olfactory projection to the pyriform cortex en route to the entorhinal and perirhinal cortices links the odor to the visual and auditory memories. Sensory input is combined and stored by the structures of the medial temporal lobe Access to names of things from memory 24 2. Affective Responses and Spatial Navigation The affective response is the subjective feeling about the stimulus Affective response involves the amygdala in the medial temporal lobe Associates the stimulus with positive, neutral, or negative consequences Following damage to the amygdala, animals do not have an emotional response to threatening stimuli 25 3. Spatial Navigation Hippocampus contains place cells to encode location in space and 26 27 25 3. Spatial Navigation Hippocampus contains place cells to encode location in space and support navigation These cells allow you to navigate in space and to remember where you are. 26 Neural Pathways for Face Processing 27 Superior Temporal Sulcus Superior temporal sulcus (STS) detects biological motion, which is movement of relevance to the species our eyes, faces, mouths, hands, and bodies make movements that can have social meanings Understanding the intentions of others is an important part of social cognition, which depends on multimodal integration in the STS Body motion, facial movements, and voice cues enable us to recognize people from a safe distance and enable us to infer the intentions of others Cells in STS are sensitive to mouth movements and vocal characteristics Other cells are responsive to body motion in a particular direction or to particular facial expressions 28 Neuronal Sensitivity to Movement Direction 29 Visual Processing in the Temporal Lobe When studying brain activity associated with complex visual scenes from movies, multiple subjects showed similar patterns of activity in auditory and visual regions of the temporal lobe Different types of scenes from the movie, such as close-ups of faces versus landscape scenes, activated different parts of the brain, FFA & PPA Within the frontal and parietal lobes, there was little similarity in patterns of brain activity between subjects Therefore, the film clip produced remarkable coherence in sensory processing does not imply coherence among the different participants’ subjective film experiences. 30 31 participants’ subjective film experiences. 30 Brain Activity During Natural Vision 31 Visual Processing in Area TE Researchers trained monkeys to recognize complex objects to determine the characteristics required to activate cells in TE Activity in TE depends on complex combinations of features, including orientation, size, color, and texture Objects activate different combinations of cells based on the overall features they possess The similar pattern of overall activity, despite small changes in the individual objects, may be the basis for categorization Features of inferotemporal neurons: Experience and training alter the response patterns of TE neurons If monkeys shown specific objects to be remembered, neurons in TE continue to discharge in absence of the object. Visual imagery. 32 Columnar Organization in Area TE 33 Are Faces Special? In monkeys, some cells in the temporal lobe respond selectively to facial identity, and others respond selectively to facial expression Recognition of pictures is impaired if they are presented inverted, but the recognition of faces shows greater impairment, suggesting there is a selective ability to recognize upright faces There are specific cortical regions within the occipital and temporal lobes involved in recognizing upright faces Lesions to the right temporal lobe have a greater impact on the ability to process faces than do lesions to the left temporal lobe 34 Thatcher Illusionage begins at 2 m of 35 Thatcher Illusion, Inverted 36 Distributed System for Face Perception 37 38 34 35 36 Distributed System for Face Perception 37 38 Mirror, Mirror: Complains About not being photogenic? Your image of your face comes largely from looking in a mirror, where the image is reversed, whereas others have a direct view of your face. The more asymmetrical the face, the less flattering the person sees his or her image to be. Take a pic as a selfie then as a non-selfie 39 Auditory Processing in the Temporal Lobe Sound waves reaching the ear stimulate a cascade of mechanical and neural events — in the cochlea, brainstem, and eventually the auditory cortex — that result in a percept of sound. Multiple tonotopic maps exist in the temporal lobe, but the nature and function of these maps is not well understood The ultimate goal is to perceive sound-making objects, locate sound, and make movements in relation to sounds. Many cells in the auditory cortex respond to specific frequencies, often referred to as sound pitches, or to multiples of those frequencies. Two especially interesting sound types for humans are language and music. 40 Auditory Processing in the Temporal Lobe Speech perception differs from other auditory input Speech sounds come from three restricted ranges of frequencies, known as formants Speech sounds vary from one context to another, yet all are perceived as being the same Spectrogram of “d” in “deep” “deck” and “duke” are different but listener perceives them as “d” 41 42 Auditory Processing in the Temporal Lobe Speech perception 41 42 Auditory Processing in the Temporal Lobe Speech perception Speech sounds change very rapidly in relation to one another Humans normal speech 8-10 segments per seconds But, we can perceive speech at rates of as many as 30 segments per seconds! Compared to only 5 for non-speech noise Left temporal cortex Monkeys and rats with left temporal lobe damage à deficits in perceiving species-typical vocalization Speech is processed both for comprehension and for directing articulatory movements in the frontal lobe. The directing of articulatory movements is accomplished by a dorsal pathway from the superior temporal gyrus to frontal area 44 to convey phonological information for articulation and a parallel ventral pathway from the superior temporal gyrus to frontal area 45 to provide semantic information for meaning. 43 Language Perception Language is a rules-based system that enables the exchange of information Syntax is the rules of grammar, and semantics refers to the meaning of words Language can be any form of information exchange, including written language, Braille, and sign language Receptive language is taking in and comprehending information Expressive language is the ability to produce language through speech or writing or nonverbal communication 44 Music Perception While language is based on individual sound elements, music perception requires the interaction of multiple elements and the relationship between them Loudness is subjective magnitude of the sound measured in decibels Timbre refers to the distinct qualities or complexities of the sound Timbre refers to the distinct qualities or complexities of the sound Violin vs piano Pitch describes the subjective position of the sound on the musical scale and is related to frequency Related to frequency, the vibration rate of a sound wave Contributes to prosody à tone of voice 45 Frequency, Pitch, Rhythm The fundamental frequency is the lowest frequency of a note Overtones are higher frequencies included in the sound, and are generally multiples of the fundamental frequency Even when the fundamental frequency is filtered out, the auditory system can still identify it based on the overtones Rhythm (timing) is important for music perception, including the duration of the individual tones and the temporal regularity of the music (meter) Left temporal lobe is predominant for temporal grouping for rhythm Right temporal lobe is predominant for perceiving meter 46 Spectrographic Display of Middle C 47 Music and Brain Morphology Experience can change how music is represented in the brain The brains of musicians are more responsive to musical information The brains of musicians have a greater volume of gray matter in Heschl’s gyrus Increases in gray matter are correlated with musical ability Such structural differences are likely related to musical training and practice There are music-related structural differences in brain regions outside the temporal lobe, including in Broca’s area of the frontal lobe professional orchestral musicians have significantly more gray matter in Broca’s area on the left. This frontal-lobe effect may be 48 professional orchestral musicians have significantly more gray matter in Broca’s area on the left. This frontal-lobe effect may be related to similarities in aspects of expressive output in both language and music.Areas associated with the language network are also active during musical tasks 48 Music and Brain Morphology 49 Musical training is a powerful instrument for inducing brain plasticity in musicians, and it may also play an important therapeutic role in combating the effects of brain injury and aging Greater connectivity between the superior temporal gyrus and nucleus accumbens is associated with greater pleasure when listening to music. Listening to pleasurable music leads to dopamine release in the NAc and the caudate nucleus. Positive and Negative Reward Prediction Error (RPE) A small population of people (~3%) do not find music pleasurable, and although these people showed a normal reward system to a gambling game, the reward system did not respond to music. 50 Olfactory Processing in the Temporal Lobe The pyriform cortex is divided into frontal (anterior) and temporal (posterior) regions, each of which has distinct anatomical connections and functional roles The posterior portion of the pyriform cortex is contained within the temporal lobe Most olfactory studies have been conducted in rodents, not too much known in humans Posterior pyriform cortex connects with the entorhinal and perirhinal cortices and the amygdala, connecting olfactory sensations to memory and emotion 51 Asymmetry of Temporal Lobe Function Left temporal lobe 51 Asymmetry of Temporal Lobe Function Left temporal lobe Verbal memory Speech processing Right temporal lobe Nonverbal memory Musical processing Facial processing Striking overlap is revealed in the relatively minor symptoms after unilateral Dramatic effects after bilateral damage in memory and affect 52 Temporal-Lobe Networks Extensive connections between entorhinal cortex and medial temporal lobe structures support memory Synchronous activity in the hippocampus and multiple cortical regions seems to be important for the convergences of the networks Temporal-lobe language networks involve the left inferior temporal gyrus, left supplementary motor area, left thalamus, and left posterior temporal cortex Face perception involves the inferior occipital cortex and the fusiform gyrus 53 Symptoms of Temporal-Lobe Lesions 54 (1) Disorders of Auditory and Speech Perception Damage to primary auditory cortex impairs the ability to discriminate rapidly presented and complex patterns of stimuli Patients with temporal lobe damage have difficulty discriminating speech, reporting that people are talking too quickly Control subjects can identify which of two sounds comes first when they are separated by 50–60 milliseconds Patients with temporal-lobe damage need up to 500 milliseconds between sounds to correctly identify which occurred first Damage to Wernicke’s area produces aphasia, esp. left temporal Word deafness: an inability to recognize words as such despite intact hearing of pure tones. 55 intact hearing of pure tones. 55 (2) Disorders of Music Perception Patients with damage to the right temporal lobe are impaired discriminating between sounds of different pitch Difficulty discriminating between rhythms is associated with damage to the right posterior superior temporal gyrus Difficulty discriminating between musical pieces with different meters is associated with damage to the anterior temporal lobe on either side About 4% of the population has congenital amusica, meaning they are tone deaf, and this cannot be remedied by music training 56 (3) Disorders of Visual Perception Patients with damage to the right temporal lobe can describe a visual scene accurately, but they fail to notice things that are out of place, such as an oil painting in a monkey’s cage These patients also are impaired at discriminating complex patterns Such patients fail to perceive or understand subtle social cues 57 (4) Disturbance of Input Selection When multiple stimuli are presented simultaneously, the brain determines which stimulus to attend to For auditory stimuli, attention can be focused on the left or the right ear For visual stimuli, attention can be focused on the left or the right visual field Patients with temporal-lobe damage are impaired shifting attention from one stimulus to another Damage to the right temporal lobe results in bilateral deficits in attention shifting Damage to the left temporal lobe results in unilateral deficits in attention shifting 58 (5) Impaired Organization and Categorization People group objects into categories quickly and automatically Categorization is important for language and memory 58 People group objects into categories quickly and automatically Categorization is important for language and memory Damage to the left temporal lobe results in impairment in categorization Unable to place words into categories Unable to use name members of a category such as “animals” when asked Semantic categories are hierarchies of meaning in which a single word might belong to several categories simultaneously. For example, a duck belongs to the categories animal, bird, and waterfowl. Each of these categories is a refinement of the preceding one. Patients with left posterior temporal lesions may show dysphasic symptoms in which they can recognize the broader categorization but have difficulty with more specific categorizations. 59 (6) Disorders of Odor Perception and Memory Temporal-lobe seizures are often associated with olfactory auras Temporal-lobe epilepsy and surgical damage to the temporal lobe to prevent seizures result in impaired perception of odors and memory for odors 60 (7) Inability to Use Contextual Information Context is important to understanding the meaning of a stimulus (e.g., fall) Similarly, context can be important for identifying a person, and, if you see them in a different context, you may not recognize them Damage to the right temporal cortex impairs the ability of people to interpret information from context 61 (8) Memory Impairment Removal of the medial temporal lobe, including the hippocampus and adjacent cortex, resulted in anterograde amnesia, or the inability to form new memories Damage to the inferotemporal cortex interferes with conscious recall of information, and greater damage is associated with greater impairment 62 61 recall of information, and greater damage is associated with greater impairment Damage to the left hemisphere results in impairments for verbal material Damage to the right hemisphere results in impairments for nonverbal material 62 Memory Impairment Tumor in right temporal lobe Normal verbal memory Impaired on formal tests of visual memory, esp. geometric drawings 63 Look for 10 seconds, Redraw 64 65 (9) Altered Affect and Personality Stimulation of medial temporal cortex produces feelings of fear Temporal-lobe epilepsy is associated with personality changes that emphasize trivia and details in daily life Personality changes occur after damage to either lobe, but are more common after damage to the right hemisphere Temporal-lobe personality includes pedantic speech, egocentricity, perseveration, paranoia, and aggressive outbursts. Bilateral damage to the amygdala results in increased sexual behaviors (not after unilateral damage) 66 Clinical Neuropsychological Assessment Many standardized tools exist to characterize temporal-lobe function Dichotic listening and Visual Object and Space Perception Battery assess auditory and visual processing Weschler Memory Scale assess general verbal memory using multiple subtests Rey Complex Figure Test evaluates nonverbal memory by asking subjects to remember to reproduce a complex figure Token Test assesses language comprehension, but cannot narrow down the region of deficit within the left hemisphere Token Test assesses language comprehension, but cannot narrow down the region of deficit within the left hemisphere