Human Neuro 3

Orientation Columns

A column in the visual cortex that contains neurons with the same orientation preference. Cortical columns consist of neurons with the same (or very similar) orientation tuning. A column of the primary visual cortex that responds to lines of a single angle Blobs - focus on color processing Once you leave V1 or V2 it will go to either the Dorsal stream or the Ventral stream. Dorsal stream "Where" - location, movement, spatial transformations, and spatial relation. Leaves V1 and moves in a dorsal direction, up towards and into the parietal lobe. This pathway is responsible for processing the location of objects in space, spatial relationships between objects, and movement through space. Ventral stream "What" - color, texture, pictorial detail, shape, and size. Leaves V1 and moves ventrally down into the temporal lobe. This pathway is responsible for object identification, including processing stimulus features like color and shape. STS stream - a little bit of both. Bio movement (Animals humans moving). Leaves V1 and moves into a specific location in the temporal lobe called the superior temporal sulcus (hence the abbreviation, STS). This pathway is responsible for processing biological motion.

The left neglect (ignoring what happens on the left side of the world) is usually caused by:

A lesion in the right parietal lobe

Temporal Lobe

A region of the cerebral cortex is responsible for hearing and language. There are two boundaries for the temporal lobe. - Sylvian fissure (the separation between parietal and temporal and this fissure also serves as the boundary between temporal and frontal lobe) - the lateral parietotemporal line (separates the temporal lobe from the inferior parietal lobule of the parietal lobe superiorly and the occipital lobe inferiorly.) BA 41 is the primary auditory cortex (A1), with BA 42 as the secondary auditory cortex or the belt area, and BA 22 as the higher-order auditory or the parabelt area. The ventral pathway, as it leaves the occipital and enters temporal, travels through BA 37, 21, 20, and 38. This includes the ventral and STS streams and is known as the inferotemporal cortex. Remember that the STS stream processes biological motion The STS stream responds not just to people or animals, but stick figures and other images that resemble biological motion.

Frontal Lobe

A region of the cerebral cortex that has specialized areas for movement, abstract thinking, planning, memory, and judgement. The central sulcus separates the frontal lobe from the parietal lobe The sylvian fissure separates the frontal lobe from the temporal lobe The frontal lobe is large - encompassing about 20% of cortical tissue. The parietal lobe that an expansion of a particular lobe makes room for more cortical real estate, and therefore higher order cognitive functions. The only sensory system in the frontal lobe is the motor system, and primary motor (M1) is located in BA 4 (aka the precentral gyrus). The premotor cortex is anterior to M1, located in BA 6 and 8. BA 6 primarily does planning for somatic motor (muscle movements throughout the body) and BA 8 controls eye movement (the frontal eye field). BA 8 therefore gets some input from posterior parietal cortex and superior colliculi. The remainder of the Brodmann areas are considered prefrontal cortex The prefrontal cortex is the last to develop. You are born with all the cortical neurons you're ever going to have (with the olfactory bulb and hippocampus being the exception)

A1 Organization

By inserting microelectrodes directly into the brain and recording action potentials in response to carefully designed auditory stimuli, we can plot (or map) out the tonotopic organization in a variety of species, including cats, birds, and rats. Many of these species are utilized in auditory perception research. The primary auditory cortex is located within the temporal lobe (superior temporal gyrus) Tonotopic

The constructional apraxia causes people:

Can't build things

A good technique to study white matter is:

DTI

The VWFA shows specificity for print in _________:

Expert readers

A patient with a lesion in the ventral pathway can differentiate between a ball from a cube.

False

During the development of languages, statistical learning is an important process that depends on:

Important sounds in native language and grammar rules

The discontinuity theory of language suggests that:

Language appears suddenly in modern humans

Temporal cortex lesions

Many of the deficits associated with temporal cortex lesions are also associated with language, as the temporal lobe is the major hub for language.

The separation between the occipital and temporal lobes is called:

OT-Notch

Evolution of Language

Our ability to use vocal communication is not as unique as you may think - Songbirds have a complex vocal repertoire and use complex song production for use in mating and communication. The songbird brain also contains specialized regions that support these vocalizations, with some regions analogous to Wernicke's and Broca's areas in humans. What is unique in humans, is the complexity of our language - Songbird vocalizations, while complex, have a single purpose: attracting a mate or calling a parent. Human language, as you know, is used for a wide variety of purposes. Discontinuity Theory - This theory proposes that language appeared suddenly in modern humans and that this trait is thus unique to our species. Continuity Theory - This theory proposes that language evolved gradually, with hints of early language precursors present in other species.

The sulcus that separates the parietal from the occipital lobe is called:

P-O sulcus

The __________ lobe is mainly responsible for the mental rotation process.

Parietal

The lobe that can be considered as "the home" for the somatosensory systems is:

Parietal

Damage and Asymmetry

Parietal Lobe Damage: Astereoagnosia - cause by a lesion to S1 and is marked by an inability to recognize items by touch. (Have you ever felt around your nightstand in the middle of the night to look for your phone or a glass of water? You ability to identify those items in the dark, with only your sense of touch relies on S1) Afferent paresis - the loss of somatosensory feedback required for aiding in movement. This is also caused by a lesion to S1, but specific to the proprioception receptors. Awareness of the body's current state is required for planning and executing movement: you can't plan the trajectory to step up onto a ledge if you don't know where your leg is starting from! Blind touch - Individuals with blind touch are unaware of somatosensory stimulation: someone with this condition would not notice someone touching their leg when blindfolded, but would be able to point to the location of the touch if prompted. Just as blindsight was a V1 lesion, blind touch is often caused by S1 lesion. Balint's syndrome - is a bilateral parietal lobe lesion that causes an inability to fixate on visual stimuli. When fixation is possible, only one item can be processed at once (simultagnosia) and difficulty reaching for an item that requires visual processing for guidance (optic ataxia). All of the above are perception deficits and, except for optic ataxia, fall into the category of agnosias, however, because the parietal lobe is also critical for movement damage to the parietal lobe can also lead to apraxias. Ideomotor apraxia - is caused by a left hemisphere lesion and results in the inability to copy movements. Constructional apraxia - can be caused by either a left or right hemisphere lesion and results in the inability to construct physical items: they may lose the ability to complete a puzzle, build a treehouse, draw a picture

The Astereognosis (inability to recognize items by touch) is mostly caused by a lesion in:

Primary somatosensory Cortex (S1)

V1

Primary visual cortex. Also called the striate cortex. - Primary visual cortex (V1) is also known as the striate cortex. This refers to the striped organization of this brain region No high processing. Only reflects the quality of the stimuli. The information that comes from both eyes is kept separate. Once visual information leaves the primary visual cortex, it moves through the occipital lobe through several brain regions that are specialized for different features in the visual signal, such as color, shape, and movement. It was once thought that visual processing was strictly hierarchical: information went first to primary, then secondary, then tertiary areas. This is why Brodmann's areas in the occipital lobe are numbered in order (BA 17-18-19). If we injected an anterograde tracer (one that starts at the injection site and moved forward through the circuit) in one eye and then looked at V1, we would see the striping, where the cortex gets its input from the stained eye would contain the coloring. One type of organization in V1 - ocular dominance. Certain groups of neurons receive input from either one eye or the other, but not both. There are a few other types of organizations within V1. We now know that visual processing is more distributed, meaning the signal is processed in multiple areas simultaneously. This serves several purposes, but one of the most important purposes is processing speed. Parallel processing is much faster than serial processing. There are three main pathways from V1 to the rest of the brain. - Dorsal stream "Where" - location, movement, spatial transformations, and spatial relation. - Ventral stream "What" - color, texture, pictorial detail, shape, and size. - STS stream - a little bit of both. Bio movement (Animals or humans moving)

The Wernicke's aphasia is related to:

Problems in speech comprehension

The __________ is the most important boundaries between the temporal and the parietal lobe.

Sylvian Fissure

If you have a patient who is unable to differentiate the size of two objects, probably they will have a lesion in:

The Ventral pathway

Motor and Premotor cortex

The other sensory systems and their cortical areas have specific organizations. In the visual system, we saw topographic (orientation-specific) organization. In A1, we saw pitch specific organization (tonotopic). The motor cortex also exhibits specific organization. Neurons in motor cortex fire in response to direction of motion. An electrode recording from the 'hand region' of the motor strip picks up on specialization in motor neurons. In this example, the neuron under the electrode fires action potentials when the arm moves directly away from the monkey, and fires less frequently when the arm moves in other directions. Note: there are other types of specialization in the motor strip, just as there are other specializations in visual areas (remember neurons specific to color, movement, etc.?). In the motor strip, neurons are also specific to the part of the body that's moving as well as the amount of tension in the muscle. While the motor cortex (M1) is responsible for sending the commands out to the muscles, M1 doesn't plan out the movement itself. The premotor cortex, located just anterior to M1, is responsible for movement planning. While M1 is active during the movement itself, only premotor is active prior to the movement, as this region maps the muscle sequence needed for the intended action. This region is also active when watching others execute movement. When premotor cortex is damaged, either by a lesion or by a developmental disorder, this leads to problems in motor planning. For example, a monkey is trained on a task, where they are required to push a treat through a small hole in the table and catch it underneath. If they receive a premotor cortex lesion after learning this task, the monkey will lose the ability to coordinate these two movements.

Occipital Lobes

The portion of the cerebral cortex lying at the back of the head; includes areas that receive information from the visual fields. Regions of the cerebral cortex - at the back of the brain - are important for vision. - farthest away from the eyes. - It is the lobe with the least identifiable boundaries. OT notch - Separation of the occipital lobe and temporal lobe. Separates the occipital lobe from the temporal lobe on the lateral side. This is another small sulcus and can be difficult to find. PO sulcus - Separation of the parietal lobe and the occipital lobe. Not normally visible from a lateral view, normally only medial view. The calcarine fissure separates the occipital lobe from the temporal lobe on the medial side. You cannot see this fissure on the lateral surface of the brain, you must split the brain in half to see it. This is where the primary visual cortex (V1) is located. Layers of the brain 1-3 integration 4 input 5, 6 output Central Sulcus - Frontal and Parietal lobes. Sylvian fissure (Laterally) - Frontal and Temporal lobes. The occipital lobe is home to visual processing. The primary visual cortex (V1) is the first cortical site to process visual information. In terms of Brodmann's areas, V1 is referred to as BA17. Because the vast majority of connections are input, the cortical layers handling input are thickest in V1. Once we leave the primary area, output layers are thicker, since there is more passing of information happening between brain regions. For example, BA19 contains higher-level visual processing areas.

Parietal Lobes

The portion of the cerebral cortex lying at the top of the head and toward the rear; receives sensory input for touch and body position. term-23 Sections of the brain located at the top and back of each cerebral hemisphere contain the centers for touch, taste, and temperature sensations. From a lateral view, there are two boundaries - The first is the central sulcus, which separates the parietal lobe and the frontal lobe. - The second is the Sylvian fissure (also known as the lateral fissure), which separates the parietal lobe and the temporal lobe. The Sylvian fissure is also the track for a large artery, the middle cerebral artery (MCA). The MCA is the most common location of strokes in the brain. From a more medial view, there are two additional landmarks to note (two landmarks to separate parietal from temporal - one lateral and one medial.) - The first is the parietal-occipital sulcus. We discussed this marker in the last module, as it separates the parietal lobe and the occipital lobe. - The second is the posterior cingulate gyrus, which separates the ventral parietal lobe and the temporal lobe medially. Remember that there are two ways to label brain regions - by the sensory system - Brodmann's area numbers Within the parietal lobe, there are two sensory system divisions - primary somatosensory (S1) - secondary somatosensory (S2) S1 sits on the postcentral gyrus (just posterior to the central sulcus) and S2 encompasses the remainder of the lobe. The anterior Zone - 1, 2, 3, 43 - Somatic Sensations and perceptions The posterior Zone - 5, 7, 40 - Integrate sensory input (mainly somatic and visual) but also others

Movement Control

The premotor cortex is responsible for planning the movement. The premotor neurons responsible for planning specific movements are organized by the part of the body and the location on the motor strip There are two sets of systems involved in this process: cortical and subcortical. The cortical system manages the bulk of the planning of a movement. Information will pass through sensory systems as needed based on the task. - For example, if I'm picking up a basketball, I need my visual cortex to find the ball, my somatosensory system to locate where my arm is before the movement starts All of this sensory information is passed to the pre-motor cortex, which then sends the plan to M1. M1 then issues the action plan to the muscles. This is where the subcortical steps come in. There are a number of subcortical brain regions that help execute and monitor every movement command sent by M1. The basal ganglia, the inferior olive, and the cerebellum, these regions help calibrate the muscle tension needed as well as monitor the action itself for any errors.

The language network

There are more than three components to the language network. Wernicke's area - his region of the network is responsible for meaning. The exact location of this area has been under debate in the field for quite some time, but for our purposes, think about it in the dorsal posterior side of the temporal lobe. Broca's area - is named for Paul Broca, who discovered this region's purpose when a patient arrived in his office with a head injury, and could only say the word "Tan." After the patient died, an examination of his brain (see image below) revealed a significant lesion in the posterior ventral frontal lobe, in BA 44/45. Broca's area is responsible for motor planning for speech production. As in the case of the patient "Tan", individuals with damage to this region exhibit perfect comprehension of speech but struggle to produce the words themselves. Arcuate Fasciclus The white matter tract that connects the two: the arcuate fasciculus. The arcuate is a bundle of white matter fibers that connect Wernicke's area and Broca's area. Damage to this tract can cause a variety of language deficits Language researchers often measure this tract and quantify differences in the volume and organization of this fiber bundle in a variety of populations, including children with communication disorders.

Asymmetry in the frontal lobe

There is far less asymmetry in the frontal lobe. There is some asymmetry here that is worth mentioning. - First, left frontal lobe does have some language specific functions. - Second, the right frontal lobe has more of a role in nonverbal movement, like facial expressions. many frontal lobe functions are bilateral (such as knowing the time of day and decoding proverbs) or are so heterogeneous it is difficult to tell. Most frontal lobe functions are the latter: lots of different frontal lobe areas are responsible for lots of different things and it can be difficult to pinpoint. Let's talk about some of the frontal lobe's functions, in spite of the difficulty in localization them.

A Lesion in the Primary somatosensory Cortex (1) can be related to Afferent (From brain to rest of body) paresis.

True

A patient with a lesion in the dorsal pathway can differentiate between a TV from a dishwasher.

True

Affectations of the substantia nigra are involved in Parkinson's disease.

True

The Cerebellum is involved in prediction in language.

True