this produces electrical changes in outer membrane of receptor that are propagated to synaptic region of receptor where chemical transmission effect next neuron
most sensitive around wavelengths of 560 nm
most sensitive around wavelengths of 500 nm.
receive signals from and send signals to bi-polar and other ----- cells. Send signals to retinal ganglion cells
receive signals from and send signals to photoreceptors
receive signals from photoreceptors. Send signals to amacrine cells and retinal ganglion cells.
Retinal ganglion cells
communicate with bi-polar and amacrine cells. Send action potentials to brain via optic nerve.
dynamic properties - motion & flicker
static properties - texture, color, form & depth
probably involved in color
o 10% of retinal axons go to the SC o involved in controlling eye movements o involved in multi-sensory integration o sends signals bypassing V1 - may explain blindsight
-70mV, resting state, neuron said to be polarized. NA+, CL- greater outside, K+ & --protein ions inside
Excitatory postsynaptic potential (EPSP)
increases likelihood of cell firing as a result of depolarization.
Inhibitory postsynaptic potential (IPSP)
decreases likelihood of cell firing as a result of hyperpolarization.
threshold of excitation
approx. -65mV, action potential is generated.
combining individual signals into overall signal
summation of simultaneous signals around the cell
summation of signals in rapid succession
Voltage activated ion channels
open or close in response to changes in membrane potential.
Absolute refractory period
cell cannot fire again, 1-2 millisecs, followed by Relative refractory period
Relative refractory period
cell can fire with extra stimulation
AP passively conducted but is regenerated at each node along the axon
process of neurotransmitter release
binding molecule o molecules can bind to multiple receptors
o Outnumber neurons 10:1 o Recently discovered to have interesting characteristics ▪ Release chemicals ▪ Posses receptors ▪ Participate in reuptake
o increase synthesis of neurotransmitter o destroy degrading enzymes thereby increase number of neurotransmitters o increase release from terminal buttons o bind to autoreceptors to block their inhibitory effect on release o bind to post-synaptic receptors to activate them o block degradation or reuptake of neurotransmitter
o block synthesis of neurotransmitters o causes neurotransmitters to leak from vesicles thus being destroyed by degrading enzymes o blocks release of neurotransmitter molecules from buttons o activates autoreceptors and inhibits neurotransmitter release o binds to postsynaptic receptor - receptor blocker
➢ removed medial temporal lobes ➢ developed anterograde amnesia - couldn't form new memories ➢ could not consolidate explicit memories ➢ could still form implicit memories ➢ taught us about separate, localized memory systems.
➢ suffered diffuse damage including medial temporal lobes ➢ could remember general information but not autobiographical information ➢ confirmed dissociation for semantic & episodic memories ➢ also had difficulty imaging the future - mental time travel
➢ results from excessive drinking → leads to thiamine deficiency ➢ postmortem examinations reveal damage to medial diencephalon, neocortex, cerebellum & hippocampus ➢ further research identified mediodorsal nuclei damage as the source of amnesia
Alzheimer's ➢ degeneration of basal forebrain leads to reduced level of acetylcholine(ACH) in the brain. ➢ ACH depletion may contribute to -------
when reactivated, memories are reconsolidated. Susceptible to changes.
Standard consolidation theory
memories are temporarily stored in hippocampus until they find permanent storage.
Multiple trace theory
hippocampus & other structures store memories as long as they exist. Each time memory is recalled a new engram - change in the brain, is formed with a link to the previous one.
memory involving the sequence of events but not the events themselves
encodes emotional aspects of memory
Medial temporal lobe
encodes and transfers new explicit memories to LTM
principle of univarience
produce responses based on amount of energy absorbed
Priority map hypothesis
o Frontopartietal network may operate as a priority map. o Representation of the world in which objects or locations are represented by activity proportional to their attentional priority o Attentional priority combines bottom-up and top-down influences
Caused by bi-lateral damage to both parietal lobes o 3 symptoms ▪ simultanagnosia - inability to see more then one object at a time ▪ optic apraxia- severe problem in voluntary switching of fixation ▪ optic ataxia - inability to reach towards correct location of objects
inability to see more then one object at a time
severe problem in voluntary switching of fixation
inability to reach towards correct location of objects
the interval in a WM task between presentation and test, duringwhich items must be maintained in memory
the ability of an excited neuron to reduce the activation ofother functionally similar neurons within its local environment.
partly or wholly unpredictable/random.
project to parvocellular pathway in LGN -> which is thought to be color sensitive and slow-moving, important for acuity and specifically red-green channels
project to magnocellular pathway in LGN -> contrast sensitive and fast-moving
project to koniocellular pathway in LGN -> relates to color perceptoin specifically the blue-yellow channel, low acuity
first used the term plasticity to link changes in nervous paths with the establishment of habits
suggested the formation of functional association and new association paths
suggested in 1893 that the connections between neurons are possible sites of neural plasticity -learning or practice could increase the size of associated neurons, thus reducing interneuronal distance and increasing neurons' conductivity (functional capacity)
in 1898 linked neural plasticity with synaptic plasticity -expanded Tanzi's learning hypothesis -synaptic modifiability under influence of external stimulus
speculated in 1894 that learning requires the formation of new connections between neurons or the strengthening of existing connections
no external influence required
external input expected for normal development
External input required
Hubel & Wiesel
•Formation of ocular dominance columns in the visual cortex -in the presence of expected external input -refine specification -normal development
Nodes of ranvier
The gaps between the myelin sheath over axons
Ungerleider & Mishkin
Two cortical visual systems work with monkeys 1982
Optic ataxia patients lesions are found here.
Area of DF lesion.
Binkofski & Buxbaum
Divided the dorsal stream into the dorsal-dorsal for grasp and dorsal-ventral for use.
Integrated view best support!
Are image-immanent features that transiently attract attention or eye gaze, independent of a particular task. (Koch & Tsuchiya, 2007) • Bottom up (flicker, motion, color, orientation, depth, and texture)
• Focal attention: region in space • Feature-based attention • Object-based attention
Amnesia for events that occur after some disturbance to the brain. H.M. had this type of amnesia.