CH 2 Flashcards
(95 cards)
1
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Human neuropsychology
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Examines changes in behavior as a result of brain trauma
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Cognitive neuroscience
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Investigations in animals to humans and from experiments performed in the laboratory to computer simulations
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Nervous system composed of two main class of cells
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Neurons and glia
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Neurons
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cells transferring information from one place to another using electrochemical signals. Composed of dendrites [receives information from other cells], cell body [contains nucleus and other cellular components that creates enzymes and proteins that support cell functioning] and axon [appendage along which information is carried]
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Types of neurons
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Sensory, association and motor
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Sensory neuron
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Bring sensory information to CNS
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Association neuron
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Associate the sensory information with motor response within the CNS
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Motor neuron
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Send signals from the brain and spinal cord to muscles
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Glia
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support cells , outnumber neurons 10:1. Astrocytes guide communication between neurons by modifying distances between them as well as the connections between neighboring neurons. Radial glia navigate the neuron from the site of its creation to its final position in the brain. Microglia rearranges the neurons after brain injury and gets rid of dead neurons and provides structural support
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Blood-brain barrier
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Glia are critical in maintaining blood-brain barrier. Blood-brain barrier consists of tightly packed glia between the blood vessels and the neurons. This bars toxins from entering the brain, however certain nutrients and immune system cells in the bloodstream also cannot enter
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Anterior
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Front of the brain
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Posterior
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Back of the brain
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Top of brain
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Superior/Dorsal (could also mean towards the back)
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Bottom of brain
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Inferior/Ventral (could also mean towards the stomach)
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Superior
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At the top
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Inferior
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At the bottom
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Rostal
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Towards the head
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Caudal
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Towards the rear
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Medial
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Towards middle of brain
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Lateral
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Towards back of brain
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Coronal
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Separate brain from front to back
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Horizontal
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Separate brain from top to bottom
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Sagittal
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Separate left and right side of brain
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Midsagittal
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Separate from middle
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Nuclei
Distinct group of neurons whose cell bodies are all located in the same region in the thalamus
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Contralateral
On the opposite side
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Ipsilateral
On the same side
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Unilateral
One side of the brain
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Bilateral
Both sides of the brain
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Three planes used to view the brain
Sagittal, coronal, horizontal.
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Cerebrospinal fluid
Similar composition as blood plasma, brain floats in this. Present between neurons and the bony encompassment of the skull.
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Ventricles
Contains cerebrospinal fluid.
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Brain protected by skull, spinal cord protected by spinal column.
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PNS
contains all the neurons that deliver sensory information and the neurons sending signals to muscles
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Spinal cord carries the sensory information to the brain and the motor signals to be sent to the muscles.
Sensory cells lie towards the dorsal side of the spinal cord and motor cells lie towards the ventral.
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Damage to the spinal cord on the fifth vertebrae
leaves the person without control of muscles or sensations from either the arms or the legs. However, if damage is done to a lower region, loss will occur only for the bottom half of the body.
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Medulla
Directly superior to the spinal cord. Controls reflexes and respiration and heart rate.Contains 12 cranial nerves. THe region where most motor fibers cross from one side of the body to another. If brain swelling occurs which puts enough pressure on the medulla oblongata, death can happen. Also home to reticular activating system: Receives input from environment and internal milieu of body and then project diffusely to many other regions of the brain, allowing for contribution to arousal attention and sleep-wake cycles regulation.
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Cerebellum
Located posterior to medulla. Regulates muscle tone and guidance of motor activity. Damage results in loss of precision, balance, motor control and equilibrium, not paralysis. “Punch-drunk syndrome” - Person temporarily loses balance and coordination after sustaining a hard blow to the head. Lateral cerebellum allows fluidity and precision of mental processing. Also critical for discerning critical discrete temporal intervals.
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Pons
Directly superior to the medulla and anterior to the cerebellum. Acts as the main connective bridge from the rest of the brain to the cerebellum. Point of connection between most cranial nerves and brain. Serves as an important center for certain eye movement control and vestibular functions. Information from both ears converge. SOund localization.
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Midbrain
Superior to pons. Contains nuclei for some cranial nerves. Connects the inferior and superior colliculus on its dorsal side, which orients us to stimuli in the auditory and visual modalities respectively. Both these structures also help in movement of head and eyes in response to environmental stimuli - the inferior for sound and superior for large moving objects in visual periphery.
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Hypothalamus
Controls behavior to maintain equilibrium such as feeding and drinking. Damage to dorsal and lateral regions interferes with water intake. Also aids in regulation of body temperature by neurons detecting changes in temperature of skin and blood. Also has a relationship with the hormonal system (system releasing chemical messengers to target sites using the bloodstream) by directly releasing hormones in the bloodstream and indirectly causes hormone secretion of other brain regions.
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Diencephalon
contains thalamus and hypothalamus. Thalamus is a large relay center for almost all sensory and motor information coming into its cortex. Patterns of connections both from and to thalamus are very specific.
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Subcortical systems
Neural systems located in regions below the cerebral cortex. Contains basal ganglia (important for motor control) and limbic system (important for processing emotional information).
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Basal ganglia
Contains caudate nucleus, putamen, globus pallidus and nucleus accumbens (all located near thalamus). Damage to this area results in difficulty in motor control and involuntary movements. Damage to globus pallidus leads to involuntary twisting of limbs, caudate nucleus damage leads to tremors usually when the person is at rest.
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Limbic system
Series of subcortical structures forming a circuit. Includes amygdala (quick response to salient info), hypothalamus, cingulate cortex (selection of actions and motivations), anterior thalamus, mamillary body and the hippocampus (forming long-term memories).
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Cerebral cortex
Plays role in object recognition, spatial processing and attention. Physically divided into two halves, each called a cerebral hemisphere. Gyri = Hills or bumps. Sheath of neurons around brain structures. Sulci: Each valley between bumps. If deep it's called a fissure.
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Three main fissures
Sylvian, central and longitudinal
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Central fissure
Aka rolandic fissure, separates each hemisphere of the brain into an anterior-posterior dimension. Areas of the brain in front of central fissure are more involved in motor processing, those behind it more involved in sensory processing.
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Sylvian (lateral fissure)
Separates each hemisphere of the brain into dorsal-ventral. Area below this fissure is the temporal lobe (plays a key role in memory, emotion and auditory processing).
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Longitudinal fissure
Separates right cerebral hemisphere from left.
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Frontal lobe
Area in front of central fissure
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Temporal lobe
Area below Sylvian fissure
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Parietal lobe
Region directly behind central fissure but above Sylvian fissure
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Occipital lobe
Remaining region of the brain behind the parieto-occipital sulcus
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Resting potential
Difference in electrical charge between outside and inside of a neuron.
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Action potential
Sodium channels open and sodium rushes in, potassium channels open and K- rushes out. potassium ions drive neuron’s electrical change away from its resting potential [-70 millivolts]. When the cell ‘fires’ [-55 millivolts], the negative charge of the neuron quite rapidly becomes positive (depolarization)[peak = +40] and afterwards the electric charge starts decreasing to reach the resting potential charge
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Hyperpolarization
After depolarization, when the charge of the neuron briefly becomes more negative than the resting potential, before coming to a rest at resting potential.
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Three properties of action potentials
1. It is self-propagating, ‘all or nothing’ (either fires or doesn’t), 2.Strength of signal doesn;t dissipate with distance 3.No other steps are involved after the charge change in order to make action potential occur
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Action potential starts from an axon hillock located where the axon meets the cell body, after which it travels to axon terminal buttons.
Here, the electric signal is converted into a chemical one. The terminal buttons contain synaptic vesicles attached to the neuron’s outer cell filled with neurotransmitters, and upon receiving the electrical signal they burst, releasing neurotransmitters in the space between the neurons (synaptic cleft).
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Synapse
Region of contact between presynaptic neuron, post-synaptic neuron and synaptic cleft.
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Receptors
Specially configured proteins embedded in postsynaptic neurons. When a neurotransmitter binds, the electrical charge is changed and the chemical signal gets turned into an electrical signal.
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Excitatory postsynaptic potential
Make the cell’s electric charge more positive, making it more likely to fire
Inhibitory postsynaptic potential: Make the cell’s electric charge less positive, making it less likely to fire
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Postsynaptic potential
The local changes in electric potentials occurring near the receptors. Could be either excitatory or inhibitory. Strength dissipates with distance, charges are small so can’t bring the neuron to fire only by one positive change, and can be either excitatory or inhibitory instead of action potential which is always excitatory.
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Two major classes of neurotransmitters
Amino acids and neurotransmitters organized into systems that fire into the cortex.
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Two main amino acids
Glutamate (excitatory effect) - epilepsy could be caused by an abnormal cell threshold lowering which makes the cell fire more often, could lead to excitotoxicity (excessive activity of neuron which could cause death for the neuron) and GABA (gamma-aminobutyric acid) [inhibitory effect] - thought to be useful for ‘fine-tuning’ activation pattern. Many substances that reduce CNS activity bind to GABA receptors. Eg: barbiturates - reduce seizure activity, induces sleep.
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Neurotransmitters organized into systems have their cell bodies located subcortically and in the brainstem and their axons diffuse throughout the cortex. Make up the cholinergic, serotonergic, noradrenergic, dopaminergic systems.
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Cholinergic
Main neurotransmitter is acetylcholine (responsible for overall cognitive excitability, attention and memory). Reduced levels are associated with less likely to fire neurons and Alzheimer’s disease. Cell bodies located in the basal forebrain nucleus diffuse to all parts of the cortex.
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Serotonergic
Main neurotransmitter is serotonin (affects sleep, mood, sexual behavior, eating, pain, memory, arousal). Affects long-term memory formation - a diet lacking in tryptophan which is used for making serotonin showed a deficit in making long-term new memories (people who take ecstasy show this deficit). Affects sleep and its stages, mood states such as depression and are treated with serotonin selective reuptake inhibitors. Side-effects of Prozac interfere with appetite, sleep and impaired sexual performance. Cell bodies located in raphe nuclei cluster of the midbrain, pons and medulla, project to hypothalamus, hippocampus, amygdala - limbic system - and striatum, cortex, cerebellum and thalamus.
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Noradrenergic
Main neurotransmitter is norepinephrine aka noradrenaline (affects arousal and attention - which is influenced by thalamus [noradrenaline stimulates thalamus for sleep and waking] and cortex). Located primarily in locus coeruleus, project to thalamus, hypothalamus and cortex, especially prefrontal cortex. Low doses of clonidine downgrades the release of noradrenaline degrades performance on attention tasks. Also bolsters emotional memory retention.
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Dopaminergic
Main neurotransmitter is dopamine. Three dopaminergic systems: nigrostriatal, mesolimbic, and mesocortical. Similarities: dopamine and noradrenaline both affect attention deficit disorders and have receptors in the prefrontal cortex, both derived from tyrosine. Serotonergic and cholinergic systems are implicated in sleep and long-term memory. Cholinergic and noradrenergic systems influence attention and memory.
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Nigrostriatal
Cell bodies located in substantia nigra, project to neostriatum. Regulates selection, initiation and cessation of motor behaviors. This is affected by Parkinson’s disease, which is associated with motor control difficulties.
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Mesolimbic
Cell bodies in ventral tegmental area, medial to substantia nigra. Linked to reward-related behaviors. Increases in response to natural reinforcement like food and also drugs and pursuit of abstract stuff like wealth.
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Mesocortical
Located in the ventral tegmental area. Axons of these cells project to much of the cortex., especially the motor, premotor and prefrontal cortex (influences working memory and executive function)
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Myelin
layer of fatty sheath. Larger sheath = faster action potential. Produced by glial cells known as oligodendrocytes by wrapping itself around the axon. More wraps = thicker myelin. White in color, so areas of the brain where this is present are called the white matter. Diseases like multiple sclerosis cause myelin surrounding a neuron to be thinned in a patchy or haphazard way with detrimental effects on motor function, cognitive function and quality of life.
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Pyramidal cell
Involved in controlling motor movements, has very good myelination to allow for fast responses.
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Fiber tract
Group of axons sending their axon to the same place
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Corpus callosum
Main fiber tract connecting both hemispheres of the brain is made of myelinated fibres.
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Primary sensory cortex
The first region in the cortex to receive information about a particular sensory modality
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Primary motor cortex
Region of cortex that is the final exit point for neurons responsible for fine motor control of the body’s muscles. Resides in front of central fissure in a motor strip (long narrow band)
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Mapping of the brain
brain functions are inverted and upside down. Feet sensors are at the top of the brain. Damage to the dorsal part of the motor strip leads to damage of the bottom half of the body.
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Hemiplegia
Paralysis on the contralateral side of the body caused by destruction of basal ganglia and motor strip.
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Primary somatosensory cortex
Portion of cortex receiving sensory information about touch, pain, pressure and proprioception. Crude touch is passed to the spinal cord, after which it does to thalamus and then cortex. Fine touch enters the spinal column, then medulla, crosses over to thalamus and then cortex.
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Primary visual cortex
First region to process visual information, specifically light and dark patterns. lEft visual field projected onto the right retina and vice-versa.
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Homonymous hemianopsia
If one hemisphere of occipital cortex is damaged, the contralateral visual field won’t detect visual information
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Quadranopia
If only the dorsal or ventral portion is destroyed, only one quadrant of the visual field is lost.
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Scotomas
Only small portions of the visual field are damaged, so light-dark contrast isn’t detected.
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Heschl’s gyrus
The primary auditory cortex (tonotopic: arranged according to frequency of tone aka pitch)of the human brain is located in the superior portion of the posterior temporal lobe
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Olfactory bulb
Located directly below the frontal lobe. Information solely ipsilaterally conveyed
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Association area
Information from multiple sensory modalities is processed here.
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Frontal lobe
Primary motor region, premotor region (involved in planning motor actions) and prefrontal region (divided into lateral - implied in executive function, working memory, language, orbital - emotional processing, medial - judgement, decision making and error detection).
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Parietal lobe
Spatial processing and attention. Associates sensory information across sensory modalities.
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Hemineglect
people neglect information coming from one hemisphere.
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Apraxia
Can’t link motor skills to ideas or representation. Alexia or agraphia (inability to read or write respectively)
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Temporal lobe
Associated with memory, visual recognition, auditory processing and emotion. Hippocampus is in this lobe. Inferior temporal visual cells respond only to highly specific visual stimuli and shapes. Damage to the temporal lobe could also lead to inability to identify sound.
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Agnosia
Modality-specific deficit (can recognise item from one sensory modality but not the other)
