Neuroscience: Cortical Organization, Brain Development, Visual Coding, and Research Methods

Comprehensive vocabulary flashcards reviewing cortical anatomy, brain injury recovery, embryological neural development, visual transduction, and neuroimaging methodologies.

Cortical Topography

The mapping of the functions of different areas of the cerebral cortex based on electrical stimulation of those areas, pioneered by Wilder Penfield.

Corpus Callosum

A large bundle of axons through which neurons in each hemisphere communicate with the corresponding part of the other hemisphere.

Precentral Gyrus

A gyrus located in front of the central sulcus specialized for the control of fine movements, such as moving a finger, primarily controlling the contralateral side of the body.

Default Network

Areas in the prefrontal cortex and temporoparietal junction that dominate activity when you do not need to concentrate on anything in particular, increasing activity during daydreaming, thinking about the past, imagining the future, or storing memories.

Prefrontal Lobotomy

A surgical procedure consisting of damaging the prefrontal cortex or cutting its connections to the rest of the cortex, often performed by Walter Freeman using tools such as an electric drill and a metal pick.

Laminae

Up to six distinct layers of cell bodies found in the cerebral cortex that lie parallel to its outer surface.

Cortical Columns

Organizations of cortical cells arranged perpendicular to the laminae, wherein neurons within the same column share similar functional response properties.

Striate Cortex

The primary visual cortex located at the posterior pole of the occipital lobe, named for its striped appearance in cross-section.

Postcentral Gyrus

The primary somatosensory cortex situated in the parietal lobe behind the central sulcus, receiving sensations from touch receptors, muscle-stretch receptors, and joint receptors across four cellular bands.

Kluver-Bucy Syndrome

A behavioral condition resulting from temporal lobe damage characterized by diminished fear and anxiety, placing unsuitable objects in the mouth, overeating, and maladaptive sexual behaviors.

Binding Problem

The large-scale integration problem concerning how various sensory areas of the brain combine signals to produce a unified perception of a single object.

Neurogenesis

The process of forming new neurons in the nervous system, occurring in adult regions such as the subventricular zone, the dentate gyrus of the hippocampus, and the striatum.

Subventricular Zone (SVZ)

A lining along the lateral ventricles containing Type A cells (new neurons), Type B cells (astrocytes), and Type C cells (proliferative precursors) that maintains neuroblast production into adulthood.

Brain-Derived Neurotrophic Factor (BDNF)

A major growth molecule supported by exercise and diet that binds presynaptically and postsynaptically to TrkB receptors to enhance synaptic transmission, gene transcription, and neuronal resilience.

Hormesis

A biological phenomenon, also known as preconditioning, in which exposing cells and organisms to mild stress results in adaptive responses that protect against more severe stress.

Ischemia

The most common form of stroke, caused by a blood clot or other arterial obstruction that deprives brain cells of oxygen and glucose.

Excitotoxicity

Cell death caused by the overstimulation of nutrient-deprived neurons, resulting from impaired ion pumps, massive glutamate release, and excessive calcium influx through NMDA receptors.

Tissue Plasminogen Activator (tPA)

A clot-dissolving drug administered to relieve ischemia and restore blood flow, ideally given within $3$ to $4.5\,\text{hours}$ following stroke onset.

Diaschisis

The decreased physiological activity of surviving neurons in intact brain areas following damage to other neurons from which they normally receive input.

Collateral Sprouts

New branches formed by undamaged axons that take over vacant synapses after a target cell loses its normal axonal input, induced by secreted neurotrophins.

Denervation Supersensitivity

A compensatory adjustment where remaining synapses become heightened in sensitivity and more easily stimulated following damage to incoming axons.

Phantom Limb

A continuing sensation of an amputated body part that arises when alternate inputs (such as axons representing the face) sprout into vacant cortical regions previously devoted to the lost limb.

Homeobox Genes

A series of genes sharing a large sequence of DNA bases that regulate the expression of other genes and control early anatomical axis development in embryos.

Neural Darwinism

A developmental principle stating that the nervous system begins with more neurons and synapses than it can retain, keeping only the most successful combinations through competitive selection.

Nerve Growth Factor (NGF)

A neurotrophic protein discovered by Rita Levi-Montalcini that is delivered by target muscles to promote axon survival and cancel programmed cell death.

Apoptosis

A programmed cellular mechanism of self-destruction that occurs when a developing neuron fails to receive sufficient neurotrophic support or synaptic input.

Radial Glia

Specialized glial cells forming a structural scaffolding from the ventricular zone to the surface of the cortex, along which migrating neurons travel.

Focal Hand Dystonia

A condition known as musician's cramp where extensive practice causes overlapping reorganization of cortical finger representations, resulting in involuntary muscular contractions.

Fovea

A central retinal region roughly $1.5\,\text{mm}$ in diameter, densely populated with cones and specialized for acute visual perception under daytime lighting conditions.

Optic Disc

The region at the back of the eye through which blood vessels and ganglion cell axons exit, forming a blind spot due to the total absence of photoreceptors.

Myopia

A refractive condition (nearsightedness) where light focuses in front of the retina due to an elongated eyeball distance, which can be protected against in childhood by spending time under light levels of at least $10{,}000\,\text{lux}$.

Rhodopsin

A photopigment embedded in the lamellar discs of rod photoreceptors, composed of an opsin protein and the light-absorbing molecule retinal.

Dark Current

The steady inward flow of positive ions through open cGMP-gated channels that maintains rod photoreceptors in a depolarized state in the absence of light.

Centre-Surround Receptive Field

A concentric receptive field arrangement in bipolar and ganglion cells wherein illuminating the center produces an effect opposite to illuminating the periphery, mediated by horizontal cells.

Parasol Cells

Retinal ganglion cells (M cells) with large receptive fields, fast axon conductance, and low spatial frequency sensitivity that project to magnocellular layers to process movement.

Midget Cells

Retinal ganglion cells (P cells) with small receptive fields and slow axon conductance that project to parvocellular layers to convey high spatial frequency and red-green color details.

Geniculostriate Pathway

The primary visual pathway running from retinal ganglion cells through the optic chiasm to the lateral geniculate nucleus of the thalamus, and continuing to primary visual cortex (V1).

Simple Cells

Cortical feature detectors in the primary visual cortex identified by David Hubel and Torsten Wiesel that display distinct, fixed excitatory 'on' and inhibitory 'off' zones responsive to bar orientations.

Blindsight

The phenomenon wherein individuals with damage to the primary visual cortex report no conscious visual perception yet are able to accurately point toward or identify features of objects in their blind visual field.

Stereotaxic Instrument

A precision surgical device used to locate deep subcortical brain structures by securing the head and positioning electrodes or cannulae relative to skull landmarks such as bregma.

Bregma

The anatomical junction point of the coronal and sagittal sutures on the mammalian skull, utilized as a primary reference coordinate during stereotaxic surgery.

Sham Lesion

A control surgical procedure that performs every preparatory step of an experimental brain lesion without passing the destructive electrical current or delivering the neurotoxin.

Transcranial Magnetic Stimulation (TMS)

A non-invasive technique that applies intense, brief magnetic pulses to the scalp to temporarily inactivate cortical neurons underneath the coil, producing a transient 'virtual lesion.'

Optogenetics

A method developed by Karl Deisseroth using light-sensitive ion channel proteins delivered by viruses into targeted neurons, enabling optical stimulation or inhibition via fiber optics.

Electroencephalograph (EEG)

A device that records average electrical wave patterns of populations of cortical neurons beneath electrodes placed on the scalp, offering high temporal but poor spatial resolution.

Magnetoencephalography (MEG)

A brain imaging method that measures the faint magnetic fields produced by neuroelectric currents using Superconducting Quantum Interference Devices (SQUIDs), yielding millisecond temporal resolution.

Positron-Emission Tomography (PET)

A functional neuroimaging technique that tracks metabolic activity by detecting pairs of gamma rays produced when positrons from injected radioactive glucose collide with nearby electrons.

Functional Magnetic Resonance Imaging (fMRI)

A neuroimaging method that uses the Blood Oxygenated Level Dependent (BOLD) signal to map active brain areas by detecting differences in magnetic susceptibility between oxygenated and deoxygenated hemoglobin.

Diffusion Tensor Imaging (DTI)

A specialized magnetic resonance method that maps the trajectories of white matter axon bundles by measuring the anisotropic diffusion of water molecules along nerve pathways.