chapter 2 6 medium questions

Introducing the Brain

• Neurons are cells that make up the nervous system, consisting of a cell body (soma), dendrites, and axon.
• The cell body contains the nucleus and organelles.
• Neurons receive information through dendrites and send information through the axon.

Neural Communication

• Terminal buttons of a neuron and dendrites of another neuron communicate through a small gap called a synapse.
• The presynaptic neuron is the information giver, and the postsynaptic neuron is the information receiver.
• The presynaptic neuron is electrically charged by an action potential, which reaches the terminal buttons and induces the release of informative chemicals called neurotransmitters.

Directions and Sections of the Brain

• Lateral refers to the outer regions of the brain.
• Medial refers to the central regions of the brain.

Gross Organization of the Brain

• Gray matter consists of cell bodies.
• White matter consists of axons and glia (support cells involved in tissue repair and myelin formation).
• White matter tracts are bundles of axons.

Ventricles

• No specific information provided.

Cerebral Cortex

• The cerebral cortex is composed of folded sheets of gray matter.
• Raised surfaces are called gyri (gyrus), and folds are called sulci (sulcus).
• The 4 main parts of the cerebral cortex are not specified.

Gyri and Sulci

• The folded structure of the cerebral cortex helps increase the area/volume ratio, making it more efficient in packaging.

Subcortex

• The subcortex is a gray matter collection located under the white matter.
• It consists of the basal ganglia, limbic system, thalamus, and hypothalamus.

Basal Ganglia

• The basal ganglia are involved in motor control and skill learning.
• Disorders associated with the basal ganglia include poverty or excess of movement, such as Parkinson's and Huntington's diseases.

Limbic System

• No specific information provided.

Diencephalon (Thalamus & Hypothalamus)

• No specific information provided.

Midbrain & Hindbrain

• No specific information provided.

Sensation and Perception

• Sensation: the effect of a stimulus on sensory organs
• Perception: the interpretation of a stimulus based on prior experience, with the brain actively constructing a visual representation of the world

From Eye to Brain

• Rod cells: specialized for low light intensity and movement detection
• Cone cells: specialized for high light intensity and color information
• Fovea: entirely made of cones, responsible for visual acuity
• Blind spot: where the optic nerve leaves the eye
• Geniculostriate pathway: the most understood pathway, making the largest contribution to human visual perception

Primary Visual Cortex (V1)

• Located in the occipital lobe, responsible for visual processing
• Hubel and Wiesel's experiment: single cell recordings in cats, discovering simple, complex, and hypercomplex cells
• Simple cells: respond to particular orientations and single points of light
• Complex cells: respond to movement of orientation, larger receptive fields
• Hypercomplex cells: respond to orientation and length, enabling construction of complex visual information

Cortical and Non-Cortical Routes

• ~10 pathways discovered, with the geniculostriate pathway being the most understood
• Other routes are evolutionarily older and provide information about time of day, orienting stimuli, etc.

Problems with Primary Visual Cortex

• Retinotopic organization: layout of receptive fields in V1 reflects spatial organization of the retina
• Hemianopia: cortical blindness restricted to one half of the visual field
• Quadrantanopia: cortical blindness restricted to a quarter of the visual field
• Scotoma: a small region of cortical blindness

Blindsight

• Inability to report perceiving visual stimuli, but performance suggests otherwise
• Case of DB: reported not seeing stimuli but oriented his eyes correctly towards stimuli

Extrastriate Areas in Vision

• V4: associated with color perception and color constancy
• Achromatopsia: failure to perceive color due to damage to V4
• V5 (or MT): associated with motion perception
• Akinetopsia: failure to perceive visual motion due to damage to V5

Object Recognition

• 1. perception of basic elements (edges, contrasts, orientations)
• 2. grouping physical elements (depth cues, divide surfaces)
• 3. viewer-centered description matched onto stored 3D descriptions of objects
• 4. meaning attributed to the stimulus

Agnosia

• Apperceptive agnosia: failure to recognize objects due to deficit at the level of object perception
• Associative agnosia: failure to recognize objects due to deficit at the level of semantic memory
• Case of HJA: impaired at deciding if objects are real or made up, and naming objects

Categorical Perception

• Category specificity: different categories represented differently in the brain
• Parahippocampal place area (PPA): responds to scenes more than objects
• Extrastriate body area (EBA): responds to the human body more than faces, scenes, or objects

Face Recognition

• Fusiform face area (FFA): responds more to faces than other visual objects
• Prosopagnosia: inability to recognize previously familiar faces