CSB332 Lecture 15 Notes

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University of Toronto St. George
Cell and Systems Biology
Francis Bambico

CSB332 Lecture 15 Slide 3 - Rote learning might underlie the psychological reality behind non-associative LTP. Rote rehearsal might be explained by these changes in the hippocampus referred to as non- associative LTP. - If you are able to associative the narrative to a more meaningful context, then you can increase the capacity of your memorization. Meaningful learning might underlie the psychological reality behind the hippocampal changes associated with associative LTP. Slide 7 - This represents a moderate stimulation associated with a lower type of stimulation because the image is still not familiar to you. You don’t get exposed to this image very often and you don’t see this image in the real world. The image is not as strong of stimulation. In order for you to increase your memory or consolidation of the narrative, then you would have to repeat the pairing over and over again. You have to pair the image with the narrative before you increase your ability to memorize the narrative. Slide 9 - The association can be between a strong emotion experienced at the time when an event occurs. The emotion evoked by the twin tower attack is likely information that is coming from the amygdala, which is where processing of emotional experiences occur. The pathway is highly activated with the experience of a strong emotional event and when you associate it with another event that mediates a weak stimulation, then you can still recall the weak stimulation (e.g., what you were doing when the twin tower attack occurred). This is called flashbulb memory. Slide 10 - Extreme emotions and severe stress could impair and severely affect memory consolidation/formation. Slide 11 - Non-associative and associative LTP are processes that occur in the brain. How is the brain able to associate different events/percepts/information? How does the brain associate new information with information already stored in memory? This is via higher order processing called cortical/cognitive processing. This is possible because the brain consists of association areas. Slide 12 - Only a small portion of the brain is devoted to primary sensory processing (e.g., smell, taste, motor cortex, and vision). The association areas are also adjacent to the different lobes of the brain that are also responsible for multi-sensory/multi-modal association. Slide 13 - This is a brain with the different association areas. The deep white matter structures allow for the communication for the different cerebral regions of the brain. Under the superficial gyri layers of the brain, you will find a large network of association fibers that allow for intra-cerebral synaptic connectivities between different areas of the brain. Slide 14 - Superior longitudinal fasciculus allows for the communication between the frontal region and the posterior region. - Frontotemporal and arcuate fasciculus allows for the communication between the frontal areas of the brain and the temporal regions of the brain. - Inferior occipitofrontal fasciculus allows for the communication between the interior frontal areas and the occipital cortex. - Uncinate fasciculus allows for the communication between the frontal regions and the anterior temporal lobe. - Cerebral arcuate fibers (e.g., U-shaped fibers) allows for the communication between neighbouring gyri or more superficial/lateral regions of the brain. Slide 15 - Association fibers allows for communication between neighbouring regions within the same hemisphere. Commissural fibers allow for communication of two similar/homologous regions of the left and the right hemispheres of the brain. Slide 16 - When light stimulus enters the eyes, the image is flashed onto the retina, information is relayed from the retinal ganglion axons that make up the optic nerve, information from the optic nerve is relayed to optic chiasm, then optic tract, then the lateral geniculate nucleus of the thalamus, which is the major sensory relay station of the brain. Neurons in the thalamus send axons containing visual information to the visual cortex. - The visual cortex is subdivided into the striate cortex, which is the primary visual cortex. It gets information received from the visual stimulus about color, form, motion, movement. V1 sorts that information and sends some of the cataloged information dorsally and ventrally. There are two streams coming from the primary visual cortex. Information about form and motion propagates along a dorsal stream. Information about color and form propagates along a ventral stream. Slide 17 - The dorsal stream and the ventral stream are polysynaptic axons. It is composed of many synapses. In the dorsal stream, the information is delivered to the terminal regions in the parietal cortex. In the ventral stream, the information is delivered to the infero-lateral and infero-medial temporal cortices, which also contains the hippocampus. o Dorsal stream = motion, location of the visual stimulus o Ventral stream = color, form, identity of the visual stimulus - Akinetopsia is the inability to perceive movement. The person is only able to see snapshots of certain scenarios. They are not able to perceive movement and motion of stimuli. - Hemineglect is a condition when the person is able to perceive/identify the object, but the person is unable to locate the object in 3D space. It might have something to do with the distortion of the mental representation of 3D space. It might have something to do with the impairment in attention such that the person isn’t able to pay attention to a specific stimulus at a given time. - Visual agnosia (e.g., psychic blindness) is the inability to identify/name the object, but the ability to perceive where the object is. The person is able to avoid the obstacles in a hallway without incurring any injury. - Prosopagnosia is the inability to identify familiar faces (e.g., loved ones, relatives). The anterior region of the gyrus in the inferior temporal cortex called the fusiform gyrus is damaged. Slide 18 - The fusiform face area responds to faces. The parahippocampal place area responds to being in different places at a given time. - This is an fMRI scan of monkey’s brain. The researchers wanted to identify the exact region of the temporal lobe that is responsive to faces. They showed the monkey both human and monkey faces. They were able to pinpoint a region that is analogous to the fusiform area in humans located in the anterior region of the inferotemporal lobe (labelled in yellow and red) that are responsive to faces. Then they wanted to determine whether the neurons in the area are responding specifically to facial stimuli. After they identified the structure, they lowered an extracellular recording electrode into the fusiform face region and they recorded from different neurons in the region while showing different visual stimuli. - These are the responses of the neurons in the fusiform face area. The neurons increase their firing activity if they have been shown pictures of faces of human and monkey. One bar corresponds to one individual neuron. These neurons do not respond or have a low response to stimuli from different mental categories (e.g., pictures of bodies, fruits, gadgets, etc.). The neuron only specifically responds to faces. - When information is received by the inferotemporal cortex, the image/percept is cast on the inferotemporal cortex and the brain compares the image/percept to stored information already in the inferotemporal cortex. There are templates of images already stored in the inferotemporal cortex. The brain compares the new visual stimulus with information stored in the inferotemporal cortex. o There are two possibilities.  The brain compares the percept with stored information about definitional features (e.g., features about a specific mental category). It analyzes the features of the percept and compares it to a checklist of a few features that are stored in the inferotemporal cortex that are necessary and required. Definitional features are necessary and required features. It is an all-or-none categorization or concept formation. The visual stimulus needs to contain all
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