Group B2: Praveena Simonpillai, Koral Neil,
Katelyn Pirie, Pavi Nantheeswarar,
Sara Silva, and Nakul Ratra
Module 2: Memory for spatial locations, motor responses, and objects: triple dissociation
among the hippocampus, caudate nucleus, and extrastriate visual cortex
Raymond P. Kesner, Bridget L. Bolland, Manoli Dakis
Two Major Theoretical Views concerning the neurobiological basis of memory for new info:
1) Working and Declarative Memory Model:
Hippocampus exclusively mediates or codes all info (spatial, temporal, response, sensoryperceptual, or affect)
2) Attribute/ Data-based Memory Model:
There are different neural substrates that mediate different attributes.
Purpose of the Current Study:
To determine which of the two previously mentioned models supports the neurobiological basis of
memory for new info by testing working/data-based memory for 3 different memory tasks (spatial
location, response, and visual object)
Hypothesis:
1) Based on Working and Declarative Memory Model:
 Predict a deficit on all 3 tasks for rats that received hippocampal lesions, but no deficits for rats
with caudate or extrastriate visual cortex lesions.
2) Based on Attribute/Data-based Memory Model:
 Predict a deficit for hippocampal-lesioned rats only in the memory for spatial location task.
 Predict a deficit for caudate nucleus-lesioned rats only in the memory for motor response task.
 Predict a deficit for extrastriate visual cortex-lesioned rats only in memory for visual object
task.
Experiment 1-Spatial location recognition memory task:
Step 1 – Training Phase:
• Familiarized with maze
• Trained using a delayed spatial matching-to-sample procedure
Step 2 – Study Phase:
• Rats trained to enter a randomly selected arm of the maze to obtain a small piece of cereal
(reinforcement)
• Rat returned to centre area, linoleum was wrapped around the central platform to cover all arms
Step 3 – Test Phase:
• Linoleum was removed and rat was given choice between previously entered arm and a new
arm
• After reaching criterion performance (75% correct or better on 16 consecutive trials) rats
received either hippocampal lesions, caudate nucleus lesions, extrastriate visual cortex lesions,
or cortical control
After Surgery:
• Retested 4 times daily until reached criterion performance again
• 32 trials (4 per day) with 15 second delay between study and test phase
• 32 trials with 30 second delay between study and test phase
Group B2: Praveena Simonpillai, Koral Neil,
Katelyn Pirie, Pavi Nantheeswarar,
Sara Silva, and Nakul Ratra
Experiment 2 -Motor response recognition memory task:
Step 1 - Training phase:
• Familiarized with maze
Step 2 - Study phase:
• Rat place in middle arm and given opportunity to make left or right turn depending on which
door was opened
• Given reinforcement for making the right choice
Step 3 - Test phase:
• Rat was place in middle arm opposite of the study phase arm, both left and right doors were
opened and they were given the opportunity to enter one
• Positive reinforcement for choosing the matching sample
Post Surgery:
• Rats were retested until they reached criterion or 204 trials.
Experiment 3 -Visual objects recognition memory task:
Step 1: Training Phase
• Familiarization with apparatus
Step 2: Study Phase
• Side one of apparatus, rat given opportunity to push aside visual object to obtain reinforcement
• On other side, rat must choose novel unique object in order to receive reward (“win-shift” or
nonmatching-to-sample rule)
• 10 trials per day are given to each rat until 75% criterion or better on 60 consecutive trials has
been reached
Step 3: Test Phase (After Surgery)
• Recovered rats are retested daily with 10 trials per day until 75% criterion or better on 60
consecutive trials has been reached
• 10s and 20s delay trials done after until criterion reached or after 260 trials
Results:



Hippocampal lesioned rats impaired in spatial location memory task only
Caudate nucleus lesioned rats impaired in response memory task only
Extrastriate visual cortex lesioned rats impaired in visual object memory task only
Conclusion:
 Triple dissociation among hippocampus, caudate nucleus, and extrastriate visual cortex in
mediating working/data-based memory for spatial location, response, and visual object
information, respectively – systems work independently and in parallel
 Results support Attribute/Data-based Memory model – need for a multidimensional model
 Refuted hypothesis 1 but hypothesis 2 was supported