What is working memory?
the ability to keep something active in one’s mind for a short period of time
Give examples of working memory
- being able to remember a phone number long enough to dial it
- holding the steps of a maths problem in mind as you solve it
- liistening and comprehending a long sentence
What is the difference between working and long-term memory?
- working is used for immediate processing and manipulation of information
- long term is used for storing information over an extended period
Describe the experiment used to distinguish working memory from long-term memory
- subjects are asked to briefly remember a string of digits
- normal controls learn to remember long strings, because they can use working and long-term memory
- patients with MTL lesions never learn to remember long strings, because they only have working memory, which has a limited capacity
What tasks use working memory?
those that require several intermediate steps and are interrupted by distractions
How does the PFC contribute to working memory?
- maintains information in an active state even in the absence of external stimuli
- integrates information from different sources to allow for decision making and problem solving
How does the PFC contribute to goal-directed behaviour?
- involved in planning and decision making to help formulate strategies to achieve desired outcomes
- behavioural flexibility when circumstances change
- top down control
What is top-down control?
PFC exerts control over other brain regions to align actions with goals which ensures that behaviour is guided by internal goals rather than immediate external stimuli
How can visual input enable the PFC keep a visual scene in working memory?
via the dorsal and ventral visual streams
What can communication with the MTL allow the PFC to do?
control which short-term memories get backed up in long-term storage
Give an example of a working memory task
- decide if an initial sound is the same as a test sound with either a silent delay between or pure tone distractors
- patients with a prefrontal lesion were unable to complete the task with distractors
What is the neural basis of working memory?
neurons in the PFC continue to fire and maintain information about a stimulus during a delay period
What is the IPSC reversal potential and decay time of GABA A receptors?
- reversal potential = -70mV
- decays in ~50ms
What is the IPSC reversal potential and decay time of GABA B receptors?
- reversal potential = -90mV
- decays in ~300ms
When does AMPA receptor conductance increase?
when presynaptic excitatory neurons release glutamate
When does GABA A receptor conductance increase?
when presynaptic inhibitory neurons release GABA
What happens as AMPA receptor conductance increases?
the neuron membrane potential is pulled towards the AMPA reversal potential
What happens as GABA A receptor conductance increases?
the neuron membrane potential is pulled towards the GABA reversal potential
