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Human amnesia and animal models of amnesia: performance of amnesic patients on tests designed for the monkey
L R Squire1, S Zola-Morgan, K S Chen
1Veterans Administration Medical Center, San Diego, California 92161.
Abstract:
The performance of amnesic patients was assessed on five tasks, which have figured prominently in the development of animal models of human amnesia in the monkey. The amnesic patients were impaired on four of these tasks (delayed nonmatching to sample, object-reward association, 8-pair concurrent discrimination learning, and an object discrimination task), in correspondence with previous findings for monkeys with bilateral medial temporal or diencephalic lesions. Moreover, performance of the amnesic patients correlated with the ability to verbalize the principle underlying the tasks and with the ability to describe and recognize the stimulus materials. These tasks therefore seem to be sensitive to the memory functions that are affected in human amnesia, and they can provide valid measures of memory impairment in studies with monkeys. For the fifth task (24-hour concurrent discrimination learning), the findings for the amnesic patients did not correspond to previous findings for operated monkeys. Whereas monkeys with medial temporal lesions reportedly learn this task at a normal rate, the amnesic patients were markedly impaired. Monkeys may learn this task differently than humans.
Insights
Amnesic patients showed memory impairments on four tasks used in animal models, correlating with verbalization abilities. However, findings differed for one task, suggesting distinct learning mechanisms between humans and monkeys.
Area of Science:
- Neuroscience
- Cognitive Psychology
- Comparative Psychology
Background:
- Animal models are crucial for understanding human amnesia.
- Medial temporal and diencephalic lesions in monkeys inform human amnesia research.
- Assessing amnesic patients on tasks used in animal models can validate these models.
Purpose of the Study:
- To evaluate amnesic patients on tasks commonly used in monkey models of amnesia.
- To determine if these tasks are sensitive to memory deficits in humans.
- To assess the cross-species validity of animal models for human amnesia.
Main Methods:
- Amnesic patients completed five memory tasks previously used with monkeys.
- Tasks included delayed nonmatching to sample, object-reward association, and concurrent discrimination learning.
- Performance was correlated with verbalization and stimulus recognition abilities.
Main Results:
- Patients were impaired on four of the five tasks, consistent with monkey lesion studies.
- Performance correlated with the ability to verbalize task principles and recognize stimuli.
- Patients showed marked impairment on 24-hour concurrent discrimination learning, unlike monkeys.
Conclusions:
- The studied tasks are sensitive to memory impairments in human amnesia.
- These tasks can serve as valid measures for memory deficits in monkey studies.
- Differences in 24-hour concurrent discrimination learning suggest species-specific learning processes.