Introduction to Behavioral Psychology and Sensory Processing

Glutamate

The most common neurotransmitter found in the nervous system, its excitatory because glutamate receptors induced depolarization after neurotransmitter binding.

GABA

The most common inhibitory neurotransmitter, causes IPSPs.

Acetylcholine

Usually excitatory, present in both peripheral and central nervous system at the neuromuscular junctions which are synapses between motor neurons and muscle fiber.

Dopamine

Movement, reward-seeking, motivation, produced in Substantia Nigra (motor function), and Ventral tegmental area (sleep regulation), can be both excitatory or inhibitory.

Serotonin

Known as 'Happiness neurotransmitter' (not that simple: sleep, appetite,...), Antidepressant drugs increase serotonin, Produced in the Raphe Nuclei, can be both excitatory or inhibitory.

Opioids

Two types are Endorphin & Enkephalin (natural morphine), Pain reduction, reward, euphoria, Mixed EPSPs and IPSPs, Bind to opioid receptors, Synthesized following pain, exercise, laughter.

Ligand

Molecules other than neurotransmitters may also act as ligands.

Agonists (presynaptic)

Enhances natural function of neurotransmitter system, stimulate release more molecules of neurotransmitters, or prolong timing of neurotransmitter release.

Agonists (postsynaptic)

Enhances natural function of neurotransmitter system, activate receptors, drug acts as neurotransmitter and binds to postsynaptic receptor, or facilitate binding of neurotransmitter.

L-Dopa (presynaptic agonist)

In Parkinson's Disease- reduced dopamine levels so want to increase dopamine with L-Dopa which is a dopamine precursor as it is eventually converted to dopamine.

Cocaine (presynaptic agonist)

Inhibits reuptake of dopamine by blocking dopamine transporter.

Amphetamine (presynaptic agonist)

Blocks and reverses dopamine transporter, Increases levels of dopamine & norepinephrine, Stimulation, euphoria, wakefulness, improved cognitive control, Treatment of ADHD, narcolepsy.

Adderall

Prescribed combination of amphetamine and dextroamphetamine.

SSRIs (presynaptic agonist)

Selective serotonin reuptake inhibitors (SSRIs) block reuptake of serotonin, Commonly prescribed antidepressant: Prozac.

Synthetic Opioids (postsynaptic agonists)

Fentanil, Carfentanil, Pain reduction, tranquilizer darts, Overdose inhibits brainstem breathing circuits.

Benzodiazepines (postsynaptic agonists)

Sedative, hypnotic, anxiolytic (anti-anxiety), anti-epileptic, muscle relaxant, Bind to GABA receptors & facilitate GABA effects by opening Cl channel even further.

Antagonists (presynaptic)

Turns off the neurotransmitter system, prevent release of neurotransmitters.

Antagonists (postsynaptic)

Turns off the neurotransmitter system, blocks receptors by binding to them.

Antipsychotics (typical)

Block D2 dopamine receptors, Prevent dopamine from activating, pimozide, haloperidol.

Antipsychotics (atypical) Antagonists (postsynaptic)

Also block serotonin receptors, But still block dopamine too

Oral ingestion

Very easy but would pass through highly acidic stomach which could break down the molecule.

Injection

Highest concentration delivered, intravenous is into blood vessel, intramuscular is into muscle tissue, and subcutaneous is into skin but above the muscle.

Inhalation

Shortest route which is why the fastest, typically for recreational purposes.

Receptor Down-regulation

Tolerance to drug, Homeostatic regulation in postsynaptic cell causes receptor degradation which means need more of drug to achieve same effect, Withdrawal in absence because Normal neurotransmitter gives low signal in comparison to drug.

Neural Sensitization

Hyper-responsive to drug, Dopamine sensitization & addiction.

Neurotoxicity

Damage to the nervous system, particularly neurons, caused by exposure to toxic substances, Amphetamine kills dopamine neurons.

Electrophysiological methods

Intracellular recording measures the membrane potential (including spikes), has a bigger amplitude, Extracellular recording measures spikes (but not the membrane potential) so cannot get depolarization/hyperpolarization that does not cause action potential, fast, actual spikes.

Optical methods

Calcium-sensitive dyes are molecules that become fluorescent in presence of calcium, More calcium -> more fluorescence meaning more relative change in potential, Indirect measurement of spikes, Slower, recording same neurons for days, and can target specific cell types.

Sensation

The activation of sensory brain pathways by a physical stimulus.

Perception

The extraction of a mental representation from sensation.

Psychophysics

How the quantitative aspects of physical stimuli correlate with the perceptions they evoke.

Psychometric Curve

Relationship between stimulus intensity (or difficulty) and the proportion of correct responses or perceptions.

Sensory Coding/Processing

How the quantitative aspects of physical stimuli correlate with the neural activity they evoke, A response in the receptor cell can evoke a response in the neurons which are synaptically connected to it.

Receptor Cell

Are specialized cells that respond to physical sensory stimuli ('Respond' = electrochemically), Receptor cells convert sensory stimuli into neural signals.

Spontaneous firing

A sensory neuron occasionally fires spikes with no (obvious) relation to any sensory stimulus, A sensory stimulus can cause the neuron to change its firing rate.

Raster Plot

Measure time of stimulus in multiple trials.

Peri-Stimulus Time Histogram (PSTH)

Avg along y axis of raster plot, spike rate per second.

Receptive Field

A sensory neuron will respond to some stimuli and not others -> selectivity, The 'receptive field' of a neuron is the region of sensory space in which a stimulus will modify the firing of that neuron.

Rate code vs temporal code

Rate is information coded by spike rate and temporal is information coded by spike timing.

Cortical maps/topography

Touch information from adjacent parts of the body are represented in adjacent parts in the cortex.

Homunculus

Homunculus ('tiny man') refers to an orderly representation of the body in the brain, areas that are more sensitive to touch get more space in our brain.

Cortical plasticity

Experience can reshape sensory representations, A monkey was trained to perform a task that required using the tips of fingers 2, 3 and 4 (1 hour per day).

Cortical Representation

Enlargement of brain area for stimulated fingers.

Phantom Limb Sensations

Feeling sensations in amputated limbs after stimulation.

Mach Bands Illusion

Enhanced contrast at boundaries of adjacent colors.

Retinal Ganglion Cells (RGCs)

Transmit visual information to the brain.

Amacrine + horizontal Cells

Facilitate lateral interactions in the retina.

Horizontal Cells

Modulate signals in the retina's lateral pathways.

Bipolar Cells

Convey signals from photoreceptors to RGCs.

Photoreceptors

Convert light signals into neural signals.

Rods

Highly light-sensitive photoreceptors for dim vision.

Cones

Less sensitive photoreceptors for color vision.

Phototransduction

Process of converting light into electrical signals.

Color Blindness

Deficiency in one or more cone pigments.

Fovea

Area for sharpest vision with highest cone density.

On-center Off-surround

RGC receptive field type enhancing center stimulation.

Off-center On-surround

RGC receptive field type enhancing surround stimulation.

Lateral Inhibition

Excited neurons reduce activity of neighboring neurons.

Edge Detection

Enhancement of contrast to identify object boundaries.

Bionic Retina

camera captures image and sends to microprocessor which converts to electronic signal and transmits to receiver, the receiver sends signal thru tiny cable to electrode panel implanted by doctors on back wall of retina, retinal implant emits the pulses which travel to optic nerve and brain receives patterns of light and dark which correspond to electrodes stimulated on retinal implant

Nasal Hemiretina

Receives visual info from outer visual field.

Temporal Hemiretina

Receives visual info from inner visual field.

Optic Chiasm

Point where visual field projections cross.

Lateral Geniculate Nucleus (LGN)

RGC axons reach the Lateral Geniculate Nucleus (LGN) of the thalamus, travel through the “optic radiation” to the primary visual cortex (V1)

Blind Spot

Area without photoreceptors where optic nerve exits.

Primary Visual Cortex (V1)

First cortical area processing visual information.

Retinotopic Organization

Spatial mapping of visual stimuli in the cortex.

Hierarchical Processing

Stepwise analysis of visual information complexity.

Blindsight

lesions in V1 which can occur due to accident or stroke, Patients report partial or complete blindness (single/both hemispheres), When asked to detect objects- appear blind but When humans forced to guess or use vision, they do well, Blindsight suggests that stimuli do not need to reach consciousness to influence behavior

Ventral 'what stream'

Responses to increasingly complex stimuli, V4 responds to complex geometric shapes, V4: first area in ventral stream to show attention modulation, IT responds to visual objects (e.g. cars), in a position-invariant and size-invariant manner

Fusiform Face Area (FFA)

Neurons in the fusiform face area (FFA) in IT respond to faces

Prosopagnosia (face blindness)

If the lesion is in FFA, can be a specific difficulty in recognizing faces

Visual agnosia

where severe and permanent impairment in learning and remembering to recognize visual stimuli

Dorsal 'where stream'

Spatial attention- guiding our view to points of interest, Using vision for guidance of actions, Detecting and analyzing movements, The dorsal stream is critical for guiding visual attention

'Change Blindness'

Occurs because we cannot pay attention to the full field of view simultaneously, where individuals fail to notice significant changes in a scene, especially when these changes occur during a brief disruption, such as a blink, saccadic eye movement, or a brief visual interruption

Saccades

Fast eye movements which focus our fovea on a small area of interest at any time

Neglect Syndrome

Unilateral lesion of the parietal lobe, Lesion in right parietal cortex (key part of dorsal stream) following stroke, Cannot guide attention to left field of view (represented in right hemisphere), Draws only right side of image

Sound Frequency

(measured in cycles per second, Hz) determines our sense of pitch, up and down

Sound Amplitude

(measured in decibel, dB) determines our sense of loudness

Pure tone vs complex sounds

A sound with a sinusoidal waveform is called a pure tone while complex sounds are multiple pure tones

Fourier Transform

decomposition of a sound (or other signal) to the frequencies that make it up

Spectrogram

shows the frequencies that make up the sound, and how they change over time

Pitch Perception

humans are 30-20,000 Hz

Pinna

collects sound & directs it down the ear canal

Tympanic Membrane

where Sound air pressure waves strike

Cochlea

Middle ear bones pass vibrations to here, coiled tube containing the basilar membrane, which vibrates with the sound wave

Basilar membrane

The basilar membrane is organized 'tonotopically', organized high to low from basal to apical end, The basilar membrane decomposes complex sounds into the component frequencies

Hair Cell Stereocilia

Vibration of the basilar membrane causes movement of hair cell stereocilia, Movement of hair cells opens K+ channels, depolarizing the cell, Depolarization causes neurotransmitter release (no action potentials), Hair cells convert sounds to electrical signals

Auditory Nerve

sends signals from hair cells to the cochlear nucleus in the brainstem

Cochlear Nucleus

first brainstem nucleus that receives auditory information from the cochlea in the inner ear. It plays a crucial role in the initial processing and transmission of sound information to higher auditory centers in the brain

Hearing Aid

A small electronic device that amplifies sounds, Three basic parts: microphone, amplifier, and speaker.

Cochlear Implant

Used in complete or near-complete deafness, Bypasses/replaces hair cell, to directly stimulate the auditory nerve

Superior Olivary Nucleus

where the cochlear nuclei send information, Brainstem nuclei critical for sound localization, Note that sound location has to be computed - it is not encoded in the peripheral receptors

Interaural Time Difference (ITD)

medial superior olive detects interaural time differences

Interaural Level Difference (ILD)

lateral superior olive detects interaural level differences

Inferior Colliculus

midbrain structure that acts as a major auditory processing hub, integrating auditory information from various pathways before sending it to the thalamus and ultimately the auditory cortex

Superior Colliculus (visual)

midbrain structure that plays a crucial role in orienting movements, particularly those related to visual and auditory stimuli.

Sensory Integration

It integrates sensory information from multiple sources and is especially important for coordinating eye movements and attention shifts in response to changes in the environment.

Auditory Cortex

Higher-level auditory processing; lesions do not cause deafness but impair recognition of complex sounds (such as speech) and impair hearing in noisy environments.

Frequency Response Area

Neurons in the auditory cortex respond to both simple and complex sounds; their receptive field can be described in a 'Frequency Response Area' (FRA).