Lecture 3 Flashcards
What are the two key aspects of attention?
Capacity limitation
Selectivity
What is capacity limitation?
– central resources for processing stimulus
inputs are limited
– resources are allocated automatically to all
stimuli until capacity is exhausted
What is selectivity?
– stimulus inputs can be prioritised based upon
their locations or elementary features (e.g.,
colour, motion)
In selectivity, inputs are prioritised based on…
locations or elementary features
What makes it more difficult to detect a target using feature based selection?
When you must focus on more than one feature of the target.
The primate visual system is…
Modular and hierarchical.
Modular system because different areas are responsive
to different type stimuli.
Hierarchical because it gets more complex.
What is the receptive field?
The sweet spot where the neuron fired the most
action potentials. That area is the receptive field.
Space where this neuron gets the most stimulation.
How can you move the receptive field?
By making eye movements.
E.g. Every time he moves his eyes, the RF moves with his
eyes. Even though eye moves to the orange figure, the
RF is now over the red stimulus.
Different coloured dots are oscillating at different
frequency. The dots will then briefly move in a
particular direction. Subjects report the direction.
Brain responds in time with the flickering of the dots.
If you look at 12hz, attend red is higher. 17 hz, attend
blue is higher.
Does attention have a benefit on a larger level than a single neuron?
Just like findings in single neuron studies, attention
gives a boost. Different brain areas turn up their rate of response when stimulus is in the
attended area.
Principles of TMS
• Stimulating coil generates a magnetic field that passes unimpeded
through the skull to induce a secondary electric current in underlying
cortex
• TMS depolarises neurons
• TMS can suppress/enhance perception, elicit phosphenes, alter
cortical excitability; useful tool for studying localization of brain
function and neural connectivity
Which site was found to be important in switching attention?
The right angular gyrus.
Two independent visual pathways into ventral parietal
region (right AG):
Pink path goes through the midbrain then thalamus
then parietal lobe. 3 synapses. FASTER.
Blue pathway has to stop at a lot of stations. 8 synapses.
What direction does the information go in the visual system?
It is not purely a feedforward system, it also feeds back. Higher areas can have an impact on the lower areas via expectation.
