Short and long-term memory processes

Question 1

GluA1 knockout

Answer 1

GluA1 knockout mice show normal SRM, but show impaired SWM. Like the other NMDA receptor manipulations GluA1 is important for forms of synaptic plasticity. It is a subunit of the AMPA receptor

Question 2

Zamanillo et al. 1999

Answer 2

The GluA1 (aka GluR1, GluR-A) subunit plays a role in the expression of long-term potentiation

Question 3

Reisel et al., 2002

Answer 3

KO of GluA1 effects spatial working memory

Question 4

Sanderson et al. 2008

Answer 4

One possible way of addressing task sensitivity is by comparing the effects GluA1 deletion with the effects of hippocampal lesions on the tasks. Mice with hippocampal lesions are impaired on both SRM and SWM tasks. Indeed they fail to performance above chance on the tasks. Therefore, both SWM and SRM are equally sensitive to the effects of hippocampal lesions. GluA1 KO mice are as bad as hippocampal lesioned mice on SWM tasks; they also perform at chance. However, they are as good as control mice on SRM tasks. This means that although both tasks are extremely sensitive to the effects of hippocampal lesions, GluA1 is necessary only for SWM.

Question 5

Schmitt et al. (2003)

Answer 5

further evidence that reference and working are dissociable. using same test and same subjects showed that GluA1 KO mice are impaired on SWM in the radial-arm maze whilst still showing normal performance on the SRM component of the radial-arm maze task.

Question 6

SWM

Answer 6

exploratory response habituates and so mouse no longer goes there. Sanderson et al. (2007) showed that GluA1 KO mice show impaired spatial habituation.

Question 7

Two forms of habituation

Answer 7

short term non-associative objects familiar simply because it has been presented recently or long term associative an object as being familiar because the context in which the object was presented helps to retrieve a memory of the object

Question 8

Sanderson, Hindley et al. 2011

Answer 8

When the effects of GluA1 deletion are tested on object recognition it was found that GluA1 deletion impairs recency-dependent object recognition, but not context-dependent recognition

Question 9

Sanderson et al. 2009

Answer 9

When tested on short-term and long-term spatial habituation GluA1 KO mice show impaired short-term habituation, but paradoxically, enhanced long-term habituation The fact that the mice showed enhanced long-term memory provides further evidence that deficits on SWM tasks cannot be due to task sensitivity. Importantly, the fact that GluA1 deletion had opposite effects on short-term and long-term habituation suggests that different, competitive psychological processes that underlie performance of spatial habituation.

Question 10

Short-term and long-term memory are competitive, interacting processes

Answer 10

GluA1 KO mouse has demonstrated that SWM and SRM are dissociable. From investigating the basis of the SWM impairment in GluA1 KO mice we have discovered that SWM likely reflects a short-term habituation process. Furthermore, short-term and long-term memory are not serial processes in which a short-term memory eventually turns into a long-term memory. Instead, short-term and long-term memory are separate, yet interacting processes. As a stimulus is experienced it will generate a memory of itself that results in the stimulus becoming familiar. As the stimulus becomes increasingly familiar mice will habituate to the stimulus and consequently reduce attention to the stimulus. If attention is reduced then this will hinder the ability to form the associations that underlie long-term habituation. Therefore, recency-dependent memory (that results in short-term habituation) will reduce associative learning (that results in long-term habituation).