Topic 9: Temporal Lobes Flashcards
Anatomy of Temporal Lobe
The tissue below Sylvian Fissure & in front of/anterior to the occipital cortex
Subcortical Temporal Lobe Structures (parts we cannot see at the surface of the temporal lobe)
- Limbic cortex
- Amygdala
- Hippocampal Formation
Lateral surface
- Auditory areas
- Ventral Stream of Visual Information: Inferior temporal cortex or - Temporal Extent (TE)
Subdivisions of the Temporal Cortex
Medial Temporal Cortex: Includes amygdala & adjacent cortex, hippocampus & surrounding cortex, & fusiform gyrus
- Posterior end of the medial temporal lobe: Parahippocampal cortex
- Parahippocampal cortex: involved in the processing of spatial and contextual information. It is particularly important for recognizing places and landmarks in our environment.
- Within the parahippocampal cortex is a specific area known as the Parahippocampal Place Area (PPA), which is selectively activated when viewing images of places, such as buildings, landscapes, or rooms. This area is thought to be involved in the encoding and retrieval of spatial information related to specific locations and environments.
- Landmark & scene recognition (sweeping scene are more activated during PPA)
Connections of Temporal Cortex
Afferent Projections (coming to the brain with sensory information: Sensory systems like auditory, visual, sensory, combination of information (multimodal)
Efferent Projections: Parietal (where things are in space) & frontal association regions, limbic system, & basal ganglia
- we see routes of auditory information to the parietal to help with auditory localization
- temporal sends frontal information, as it is the highest level of association cortex in the brain, integrating information from all lobes
- Left & Right temporal lobes Connected Via: Corpus Callosum & Anterior Commissure (smaller, lower level, the limbic system)
Five Distinct Connections
1. Hierarchical Sensory Pathway
2. Dorsal Auditory Pathway
3. Polymodal Pathway
4. Medial Temporal Projection
5. Frontal Lobe Projection
Hierarchical Sensory Pathway
- Incoming auditory & visual information
- Stimulus recognition – ventral pathways for vision & audition
- A1, A2 information is integrated, along with visual information; as we progress more interiorly through the ventral stream of the temporal lobe, the visual processing becomes more and more complex
- ventral stream also plays a role, helping us determine WHAT a sound is
Dorsal Auditory Pathway
From the auditory cortex to the posterior parietal
Detection of the spatial location of sounds and movement; sound recognition
- information from the temporal is going to go to the posterior parietal region, and that is going to help us localize the sound
Polymodal ( i.e., more than one sensory mode) Pathway
- Area under STS (superior temporal sulcus): has a role in biological motion
- Having neurons that can be cross-modal or bimodal that can process information and be active for both auditory and visual information along this pathway = From auditory & visual areas to the polymodal cortex
- Stimulus categorization & cross-modal matching
e.g., McGurk effect - example of cross-modal matching; the idea of matching the visual to the sound, we can be led to believe that we hear a certain thing when in fact, it is not what we are hearing (i.e., mouth movements influence what we hear, the visual information helps us perceive speech)
Medial Temporal Projections
From auditory & visual areas to the medial temporal lobe, limbic cortex, hippocampal formation, & amygdala
- long-term potentiation pathway: the concept that when memories are forming, in the hippocampus pathway we see physical changes in the neural network pathways
Frontal Lobe Projections
- Auditory & visual cortex to the frontal lobe
- Movement control
- Short-term memory / working memory
- Affect (emotional processing, i.e., limbic system and the frontal lobe managing our emotions and behaviour)
The temporal lobe is an important part of the brain in processing auditory and visual information. The auditory cortex in the temporal lobe is responsible for processing sound information, while the visual cortex is responsible for processing visual information. The temporal lobe also plays a role in movement control, which involves coordinating motor functions with sensory inputs.
Additionally, the temporal lobe is involved in short-term memory, which is important for holding information in mind for a brief period of time. This is especially important for tasks such as learning and problem-solving.
Finally, the temporal lobe is also involved in affect, which refers to emotions and mood. This includes the processing and regulation of emotions and the perception of emotional stimuli from the environment.
McGurk effect
e.g., McGurk effect - example of cross-modal matching; the idea of matching the visual to the sound, we can be led to believe that we hear a certain thing when in fact, it is not what we are hearing (i.e., mouth movements influence what we hear, the visual information helps us perceive speech)
Anterior Commissure
The anterior commissure and corpus callosum are both neural structures that connect the two hemispheres of the brain, but they differ in their location, size, and function.
Location: The anterior commissure is located in the anterior part of the brain, just in front of the third ventricle, while the corpus callosum is located in the middle part of the brain, above the lateral ventricles.
Size: The anterior commissure is relatively small, with a diameter of about 3-4 mm, while the corpus callosum is much larger, with a length of up to 10 cm and a width of up to 6 cm.
Function: The anterior commissure is involved in the transmission of olfactory, auditory, and visual information between the two hemispheres, as well as in the regulation of autonomic and visceral functions. The corpus callosum, on the other hand, is the main pathway for communication between the two hemispheres and plays a critical role in the integration of sensory, motor, and cognitive processes across the brain.
Theory of Temporal Lobe Function
Three Basic Sensory Functions
- Auditory input
- visual object recognition (i.e., ventral stream = object recognition)
- long-term storage of information (linking it to a percept, so we can store in memory and recognize the objects)
- columnar organization = categories of shapes stored in the brain (in image)
Sensory Processes
- Identification & categorization of stimuli
- Cross-modal matching (STS): matching visual and auditory information, e.g., ventriloquism effect; depends on the cortex of the superior temporal sulcus (STS)
Affective Responses
- Emotional responses associated with particular stimuli
- In the limbic system, the amygdala will take on the initial identification of processing, then higher cortical regions (e.g., cingulate cortex and frontal lobe) will play a higher role in processing (i.e., identifying the emotion and deciding how to control and act on it appropriately)
Spatial Navigation
- Hippocampus – explicit long-term memory and spatial memory
- Place cells discovered by O’Keefe in 1976 (i.e., place cells in the hippocampus that are very particular in responding when we are in certain areas of our environment and play a key role in allowing us to develop a cognitive map of any given environment)
- A sense of familiarity with a particular location, like sitting in the same spot every class
Place cells
- Place cells discovered by O’Keefe in 1976 (i.e., place cells in the hippocampus that are very particular in responding when we are in certain areas of our environment and play a key role in allowing us to develop a cognitive map of any given environment)
- A sense of familiarity with a particular location, like sitting in the same spot every class
Evidence for Hippocampal Place Fields
Referencing the left image: the rats are placed in this circular environment and are allowed to explore; the longer the rats are in the environment, we begin to see the “place neurons” fire very specifically when the rat is in a certain location in the environment.
- Single-cell recording in rats, over several trials that allow it to get familiar
Hippocampal place cells are neurons in the hippocampus that selectively fire when an animal is in a specific location within its environment. In other words, these cells represent the animal’s cognitive map of its environment. The discovery of place cells and their role in spatial navigation was made possible through single-cell recordings in rats.
In these experiments, researchers implanted electrodes in the brains of rats and recorded the activity of individual neurons while the rats were allowed to explore a novel environment. They found that the place neurons in the hippocampus fired selectively when the rat was in a particular location. These neurons were dubbed place cells and provided strong evidence for cognitive maps in the brain.
- when rats were placed in a larger environment with the same “floor plan,” they still saw the same firing in the place neurons in the same portion of the circle
- the initial development of the spatial specificity in the hippocampus that occurred in the smaller region was maintained, but it expanded to fit the larger circular environment
Image C, left) Fire for the left side of L/R field
Image C, right ) Area expands to a new environment
We see this in Image A and B as well
Morris Water Maze Task
The Morris Water Maze Task is a behavioural test used to assess rodents’ spatial learning and memory, particularly concerning the hippocampus. The task involves placing a rodent in a pool of opaque water and training it to find a hidden platform using spatial environmental cues. The rodent is given several trials over some days to learn the platform’s location, and its performance is measured by how quickly it can find the platform on subsequent trials when the water is opaque; therefore must rely on memory instead of visual cues.
- Train with clear water and a platform slightly above the water surface (typically do three training trials)
- Make water opaque for testing and lower the pedestal below the surface level
In the image:
B: intact hippocampus - can do in clear and opaque
C: hippocampus lesion - can do in clear but not opaque – cannot form spatial memory for external cues
Superior Temporal Sulcus (STS) & Biological Motion
Imaging (in humans) reveals activation in STS during the perception of biological motion; we see this in both hemispheres.
- e.g., dots moving on a black screen, we see a human walking (i.e., movement relevant to a species)
- mirror neurons = STS is part of the mirror neuron system, and it is important for us to perceive biological motion and use that information to guess what others intentions are (social cognition)
- theory of mind: making inferences on what the other person is thinking
Biological Motion:
- Movements relevant to a species
- Allow us to guess others’ intentions
- Social Cognition or “Theory of Mind” (mirror neuron system)
Perrett et al. (1990): human biological movement study
STS cells maximally responsive to particular types of biological motion
- single cell recording in monkeys in the STS
- showing them movement in particular movement
- there is a directional specificity to the STS, similar to motor neurons (e.g., the directional neurons experiment)
- in the first bar: directional specificity to biological motion moving towards them
Hasson et al. (2004):
Looking at activation when ppl are watching videos and looking for differences between the viewer processing sweeping scenes and movement versus processing particular objects on the screen.
- fMRI; interested in different areas of brain activation corresponding to different types of scenes
- Extensive activity in auditory & visual regions in the temporal lobe (processing auditory and visual information), in STS (processing biological motion) & cingulate regions (processing higher-order emotions)
- Correlated across 5 participants, we saw that activation across all individuals
- Selective activation to precise moment-to-moment film content (faces & scenes)
- FFA (i.e., processing faces) = lots of overlap between participants - common
- PPA (i.e., active when we see landscapes or sweeping scenes) = lots of overlap between participants - common
- Regions of the parietal & frontal lobes showed no intersubject coherence (i.e. dissociation between sensation & experience)
- not a lot of correlation between participants; the frontal lobe plays a role in higher-order processing (attention, thinking, individual differences and experience)
- variability = own subjective personal experience
Hasson et al. (2004) conducted an fMRI study where participants watched the movie “The Good, The Bad, & The Ugly” while their brain activity was recorded. They found that when participants were watching the movie freely, there was extensive activity in auditory and visual regions in the temporal lobe, as well as the superior temporal sulcus (STS) and cingulate regions. These regions were active across all five participants and were selectively activated in response to specific moments in the film, such as faces and scenes. Interestingly, the parietal and frontal lobes showed no coherence between participants, suggesting a dissociation between sensation and experience.
