Neural Information Processing – Key Points
Neural Communication
Neurons transmit signals via action potentials that travel down the axon at – m/s, then cross the synapse (~ ms total) through neurotransmitter release.
Synaptic effect is either excitatory (decreases membrane potential difference → higher firing rate) or inhibitory (increases difference → lower firing rate).
Neural Representation & Computation
Information is encoded in firing rate (continuous quantity, up to > spikes/s), not discrete states.
Cognitive operations arise from spreading activation through excitatory and inhibitory networks.
Synaptic Plasticity & Memory
Activation patterns are transient; durable knowledge is stored via long-term synaptic strength changes (more transmitter release, heightened receptor sensitivity) induced by repeated use.
Distributed vs. Local Coding
Single-cell studies reveal feature detectors (e.g., color cones, line cells; some face-responsive neurons).
fMRI evidence (e.g., Haxby et al.) shows complex items (faces, objects) represented as distributed activation patterns across cortex.
Brain Organization Basics
Cerebral cortex (≈ mm thick, ≈ cm^2 unfolded) overlies older subcortical structures.
Key orientations: dorsal/superior, ventral/inferior, anterior/rostral, posterior/caudal; planes: sagittal, coronal, horizontal.
Lobes: frontal, parietal, temporal, occipital; major landmarks include central sulcus & Sylvian fissure.
Cortical Topography
Adjacent cortical neurons map adjacent sensory/motor regions (e.g., retinotopic, somatotopic maps).
Coarse coding: each location encoded by overlapping receptive fields → patterns across many cells.
Neuroimaging Methods (Essentials)
ERPs: millisecond temporal resolution from scalp potentials.
fMRI: detects increased oxygenated blood in active areas; high spatial but limited temporal resolution; costly & restrictive environment.
DTI: traces water diffusion along axons to reveal white-matter pathways.