How do we know the brain is the seat of cognitive processes?

What did the brain evolve for?

Biology in a Nutshell *

Molecular and Cellular Neuroscience

Systems Neuroscience

Developmental Neuroscience

Techniques to study the brain

• Lesions
• Correlation of neural activity with cognitive processes
• Modification of behavior through neural stimulation

• Responding to the environment to increase reproductive success
• Brain as an accumulation of ad-hoc solutions: expect push towards behavioral perfection, but not lack of overlap, etc.

• Cajal (~1900): brain is made of discrete elements (neurons) vs. continuous theory of Golgi
• Dendrites
• Soma
• Axon
• Synapses

• Molecules
• Transmit information across neurons
• Released by pre-synaptic cell in quanta: synaptic vesicles
• Produce effect in post-synaptic cell by activating receptors
• Different receptors produce different effects, even for same NT

• Electrical signal
• Transmits information from neuronal soma to synapses in axon terminals.
• Is all-or-none (digital and binary)
• Is a voltage across cell membrane
• Produced at the spike initiation zone through synaptic input integration
• Transmitted along membrane passively following cable equation and amplified actively along the way by voltage-activated ion channels

• Molecules that constitute selective pores in neuronal membrane
• Produce currents that change voltage across membrane.
• Currents are caused by moving ions: Na+, K+, Ca++, Cl-, …
• Can be voltage-gated or ligand-gated (or none)

• Electrochemical potentials
• Na/K pump creates ionic gradient across membrane that causes hi Na+ in and hi K+ out
• Membrane at rest is polarized with inside negative
• Action potential starts with the opening of ion channels that allow Na+ to follow its electrochemical gradient
• Depolarization causes opening of K+ channels and inactivation of Na+ channels, which repolarize membrane
• Inactivation prevents ‘bouncing’ of action potential

• Most elements in blood do not enter brain
• Specific carrier molecules

• ‘Specific nerve energies’: different nerves signal different kind of stimuli (e.g. heat, cold, pain, touch)
• The paradigm of stimulus-response (Hubel & Wiesel)
• Different brain areas are responsible for different aspects of perception and behavior
• Differences in specific molecules can account for differences across individuals (e.g. rhodopsin)

• Neurons communicate via action potentials
• Taking the point of view of the organism: reading a spike train
• Periphery: reconstructing the stimulus (Bialek et al.)
• Making a decision: single neurons emulate the ability of whole monkeys (Newsome et al.)
• Periodic synchronization causes oscillations in field potentials. EEG.
• Inhibition with self-negative feedback and a fixed time-constant can generate oscillatory synchronization (Laurent et al.)
• Disruption of oscillatory synchronization impairs olfactory discrimination in bees & changes downstream neurons' response properties.

• Rods and cones
• The construction of an image
• Center-surround receptive fields

• Timpanus
• Cochlea is frequency tuned

• Visual cortex
• V1 and retinotopy
• Simple cells and complex cells: hierarchy
• MT
• V4 and color
• Color opponency
• Somatosensory cortex and the homunculus
• Auditory cortex
• Auditory neuroethology: Intensity and Phase differences
• Coincidence detection, delay lines
• Olfaction
• Multidimensional receptor space
• Pattern recognition

• Motor homunculus

• Binocular rivalry and correlation of neuronal activity with perceptual reports (Logothetis et al.)
• Perceptual ‘reality’ is a creation of the brain. Illusions. The blind spot.
• Itzhak Fried and the comic illusion
• Color constancy. Color as a mental creation which can be independent of wavelength
• Split Brain (Sperry, Gazzaniga, Bogen).

• HM
• Place cells (O’Keefe, McNaughton, Wilson et al.)