PSYCH 261 Midterm 2

Cerebral Cortex Grooves

• high surface area due to ‘raisin brain’ texture

• Fissure: Deep Groove

• Gyrus: bump or protrusion

• Sulcus: Groove or indent

• Bank of Sulcus: Side of a groove

• Fundus: Bottom of a groove

• Gray matter: Mostly cell bodies and Dendrites

• White matter: mostly myelinated axons

Cortical Laminae (layers)

6 layers in humans, 5 in mice. First layer is the outermost, the 6th layer is closer to the core regions of the brain.

Cortical Columns

Cell growths across each cortical layer. Different columns in the same area can have different functions (e.g. right eye and left eye processing).

Major grooves of the Cerebral Cortex

Central Sulcus: cuts down the side of the cortex to the halfway point, down similar to a coronal cut.
Lateral (Sylvian) fissure: Cuts diagonally from the bottom left of the brain (side view) to separate frontal and temporal lobes.
Longitudinal fissure: Fissure running down from the front to the back of the brain, separating the hemispheres.
Parieto-occipital sulcus: runs deep into the brain near the back to separate parietal and occipital lobes.
Cingulate sulcus: Sulcus within the cortex that separates the limbic lobe from the upper layer lobes.

Wilder Penfield

Corticol topography to map brain area functions based on stimulation. Sensations, images, memories.

Penfield’s (Somato)Sensory Homunculus

Postcentral gyrus (after the postcentral sulcus): left side of brain- sensory on right side; vice versa. Sensations in various parts of the body when stimulated. Area 1,2, and 3 of Brodmann’s map.

Penfield’s Motor Homunculus

Precentral Gyrus (before the central sulcus): Motor movements on right side for left side of the brain; vice versa. Motor movements in various parts of the body when stimulated. Area 4 of Brodmann’s map.

Primary Auditory cortex

Beneath the Sylvian/lateral fissure near the postcentral gyrus, at the top of the parietal lobe. Areas 41 and 42 of Brodmann’s map.

Primary Visual Cortex

Back of the occipital lobe. Area 17 of Brodmann’s map,

Brodmann’s map

map of the cortex based on cell organization.
Primary Motor cortex: area 4
Primary somatosensory cortex: areas 1,2,3
Primary Auditory cortex: areas 41, 42
Primary Visual cortex: Area 17

Frontal Lobe

Prefrontal cortex: First part of the cerebral cortex, large.
Premotor cortex: After the prefrontal cortex, more lateral
Supplementary motor cortex: Medial areas where the premotor cortex is. More prominent in saggital cross-section
Primary motor cortex: Precentral gyrus, after the premotor cortex.

Damage:
Disorganized behavior
Disinhibition/inappropriate behavior
impaired abstract thinking, rigid thought
Perseveration (ex: continue to use a plan even if its not appropriate anymore)
Personality Change
Emotional iability (ex: rapid mood shifts)

Parietal Lobe

Contains primary somatosensory cortex. Integrates sensory information, internal states (intention, proprioception), Numerical cognition.

Damage:
left- apraxia (can’t execute tasks even if they want to and are able)
right- spatial neglect

Temporal Lobe

Superior temporal: Primary and Secondary Auditory cortex, Wernicke’s area (language comprehension)

Inferior temporal: Visual object recognition, Agnosia (failure to recognize smell, objects, people, shapes (senses work fine though)), prosopagnosia (face blindness)

Medial temporal: Emotional Processing (Amygdala), Kluver-Bucy syndrome (monkeys can’t display fears/anxieties), Memory (Hippocampus). Damage in humans: epilepsy disappears and then comes back. Obsession with genitals, behavioral issues

Occipital Lobe

Right hemisphere Cuneus: Lower left visual field

Right hemisphere Lingual Gyrus: Upper left visual field

Separated by the Calcarine Sulcus

Limbic Lobe

Connected to Emotions, other limbic structures

Anterior Cingulate Cortex (ACC): Emotion, pain-related motor movements, cognitive control/error detection, reward anticipation

Posterior Cingulate Cortex (PCC): Monitoring eye movements, Spatial Orientation, Memory

Parahippocampal Gyrus: Memory

Corpus Callosum

Interhemispheric communication. Very well organized between lobes (neat wirework)

Cholinergic Systems

Neurons release acetylcholine in the basal forebrain project to the cortex and limbic system.

ACl from the pons and midbrain project to the amygdala, thalamus, brainstem, and cerebellum.
- Includes Pedunculopontine Nucleus (PPN), Laterodorsal Tegmental Nucleus (LDT)

Dopaminergic Systems

Nigrostriatal System: Dopamine from the substantia nigra, projecting to the basal ganglia.

Mesolimbic system: Dopaminergic neurons from the Ventral Tegmental Area (VTA) to limbic structures/basal ganglia (e.g. Nucleus Accumbens)

Mesocortical system: VTA to cerebral cortex

Noradrenergic systems

Norepinephrine from the locus coeruleus to various parts of the brain.

Serotonergic system

Raphe Nuclei in the brain stem project serotonin to most parts of the brain. Can be influenced by the gut.

One ionotropic, many metabotropic effects (G-Protein). Different effects due to different receptors to serotonin.

Visible Light Transmission Microscopy

Observation by shining a light into the tissue.

- Euthanization of animal, removal of brain → stabilization with chemicals; water is removed with solvent (e.g. ethanol) → hardening (e.g. parrafin) → Microtome to slice the brain → Staining.

Stains:
NissI stain- cell bodies with dyes like Methylene Blue, Cresyl Violet
Myelin stain- highlights axon bundles with dyes like Luxol Fast Blue, Osmium Tetroxide
Golgi stain- Highlights all parts of a neuron with a silver-based compound

Fluorescence Microscopy

fluorophores are inserted into a tissue to highlight a structure

Two-Photon microscopy

A laser emits two photons simultaneously. A mirror focuses them; converge onto one spot. Fluorophores emit photons in response; detected by a sensor.

Electron Microscopy

Transmission electron microscopy (TEM): electron beam passes through a tissue to hit a phosphor plate and camera array. The tissue may be stained with heavy metals.

Scanning electron microscopy (SEM): electron beam converges onto the surface of the tissue. Electron backscattering is detected with sensors.

Computer Axial Tomography

X-ray emission passes through and is detected based on absorbance by dense tissue to map structures.

Magnetic Resonance Imaging (MRI)

detailed structural views. Works with large electromagnetic coils that align protons with strong magnetic fields. Smaller perpendicular coils send radiowaves to disrupt alignment, sending radio signals that are detected. Voxels are generated to create an image.

Diffusion Tensor Imaging (DTI)

Displays only axons, showing directions based on color. Isotropic H2O movement is constrained within the axon; anisotropic movement along axons. Water movement is tracked in the region of interest.

Lesion-related techniques

Ablation- Removal or destruction of a part of a tissue; toxin or surgery

Lesion- Disruption of or damage to function of an organ- can be natural or surgery

Temporary lesion- a reversible lesion by chemical or cryogenic methods. Chemical reduces activity, cryogenic uses the cold to reduce activity.

Fiber Sparing- collateral damage when creating lesions.

Lesion-causing techniques

Aspiration- removal of a portion of a brain (e.g. by suction). Non-fiber sparing.
Excitotoxic- Killing a neuron by introducing a neurotoxin. Fiber Sparing.
Thermal- heating brain tissue to destroy it, by laser or by heating a tool. Non-fiber sparing.
Knife cut- transect brain tissue. Non-fiber sparing.
Chemical- injection of a chemical to reduce brain neuron activity. Fiber sparing; reversible.
Cryogenic- Cooling a region of the brain (cryoloop, cryotips) to reduce activity. Non-fiber sparing; reversible.

Stereotaxic surgery

Sedate rat → cut open scalp → drill hole in skull over area to be lesioned → Place rat in the stereotaxic device- get animal to bite and immobilize with ear bars → use skull plate sutures to determine locations (e.g. Bregma- coronal and saggital suture landmarks).

Sham controls- keep everything constant except for the experimental treatments.

Transcranial Magnetic Stimulation (TMS)

Intense magnetic fields to inactivate/activate neurons; temporary lesions.
Repeated stimulation (rTMS): can be used for depression, hallucinations.
Continuous theta-burst stimulation (cTMS) reduces cortical activity
Intermittent theta-burst stimulation (iTMS) increases cortical activity

Single-cell recording

Recent innovation- can screw into the brain for moving animals. Microelectrode is inserted to measure a single neuron’s activity.

Multi-cell recording: 128 Microwire array into the brain too.

Electroencephalography (EEG)