Visual implicit memory in the left hemisphere: evidence from patients with callosotomies and right occipital lobe lesions

Authors:

• Andrew P. Yonelinas

• Neal E. A. Kroll

• Kathleen Baynes

• Ian G. Dobbins

• C.M. Frederick

• Robert T. Knight

• Michael S. Gazzaniga

Date: 2001

PubMed: 11476095

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Abstract:

Identification of visually presented objects and words is facilitated by implicit memory for past visual experiences with those items. Several behavioral and neuroimaging studies suggest that this form of memory is dependent on perceptual processes localized in the right occipital lobe. We tested this claim by examining implicit mem- ory in patients with extensive right occipital lobe lesions, using lexi- cal-decision, mirror-reading, picture-fragment, and word-fragment- completion tests, and found that these patients exhibited normal levels of priming. We also examined implicit memory in patients with com- plete callosotomies, using standard and divided-visual-field word- fragment-completion procedures, and found that the isolated left hemisphere exhibited normal priming effects. The results indicate that the right occipital lobe does not play a necessary role in visual im- plicit memory, and that the isolated left hemisphere can support nor- mal levels of visual priming in a variety of tasks.

The contribution of recollection and familiarity to yes-no and forced-choice recognition tests in healthy subjects and amnesics

Authors:

• Wayne Khoe

• Neal E. A. Kroll

• Andrew P. Yonelinas

• Ian G. Dobbins

• Robert T. Knight

Date: 2000

PubMed: 10869576

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Abstract:

Recent reports suggest that some amnesic patients perform relatively normally on forced-choice recognition memory tests. Their preserved performance may re ̄ect the fact that the test relies more heavily on assessments of familiarity, a process that is relatively preserved in these patients, than do other recognition tests such as yes±no tests, which may rely more on recollection. The current study examined recognition memory using yes±no and forced-choice procedures in control and amnesic patients in order to determine whether the two tasks di€erentially relied on recollection and familiarity, and whether the extent of the recognition memory de®cit observed in amnesia was dependent upon the type of recognition test used to measure performance. Results using the remember±know procedure with healthy subjects showed that there were no substantial di€erences in recognition accuracy or in the contribution of recollection to these two tasks. Moreover, amnesic patients were not found to perform better on a forced-choice test than on a yes±no test, suggesting that familiarity contributed equally to these two types of recognition test.

The neural substrates of recollection and familiarity (pp. 468-469)

Authors:

• Andrew P. Yonelinas

• Neal E. A. Kroll

• Ian G. Dobbins

• Michele Lazzara

• Robert T. Knight

Date: 1999

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Abstract:

Aggleton & Brown argue that a hippocampal-anterior thalamic system supports the “recollection” of contextual information about previ- ous events, and that a separate perirhinal-medial dorsal thalamic system supports detection of stimulus “familiarity.” Although there is a growing body of human literature that is in agreement with these claims, when rec- ollection and familiarity have been examined in amnesics using the process dissociation or the remember/know procedures, the results do not seem to provide consistent support. We reexamine these studies and describe the results of an additional experiment using a receiver operating charac- teristic (ROC) technique. The results of the reanalysis and the ROC ex- periment are consistent with Aggleton & Brown’s proposal. Patients with damage to both regions exhibit severe deficits in recollection and smaller, but consistent, deficits in familiarity.

Recollection and familiarity deficits in amnesia: convergence of remember-know, process dissociation, and receiver operating characteristic data

Authors:

• Andrew P. Yonelinas

• Neal E. A. Kroll

• Ian G. Dobbins

• Michele Lazzara

• Robert T. Knight

Date: 1998

PubMed: 9673991

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Abstract:

Previous studies using the process dissociation and the remember-know procedures led to conflicting conclusions regarding the effects of anterograde amnesia on recollection and familiarity. We argue that these apparent contradictions arose because different models were used to interpret the results and because differences in false-alarm rates between groups biased the estimates provided by those models. A reanalysis of those studies with a dual-process signal-detection model that incorporates response bias revealed that amnesia led to a pronounced reduction in recollection and smaller but consistent reduction in familiarity. To test the assumptions of the model and to further assess recognition deficits in amnesics, we examined receiver operating characteristics (ROCs) in amnesics and controls. The ROCs of the controls were curved and asymmetrical, whereas those of the amnesics were curved and symmetrical. The results supported the predictions of the model and indicated that amnesia was associated with deficits in both recollection and familiarity.

Unilateral medial temporal lobe memory impairment: type deficit, function deficit or both?

Authors:

• Ian G. Dobbins

• Neal E. A. Kroll

• Endel Tulving

• Robert T. Knight

• Michael S. Gazzaniga

Date: 1997

PubMed: 9539232

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Abstract:

Previous research has characterized memory deficits resulting from unilateral hippocampal system damage as 'material specific', suggesting that left damage results in verbal memory impairment with preservation of visuospatial function and the converse with right damage. Implicit within this hypothesis are the assumptions that the systems are independent and memory is lateralized for each type of material. To test the verbal component of this hypothesis, unilateral hippocampal lesion and commissurotomy patients were compared with controls on a multiple-list free-recall task. The material specific hypothesis predicts severe impairment only with left lesions; right lesions and commissurotomy patients should be only minimally impaired. However, secondary memory was compromised at immediate recall for all patient groups, with both unilateral groups showing comparable and severe verbal episodic memory deficits. Final testing across all lists also revealed severe impairment in commissurotomy patients. Finding both unilateral groups to be similarly impaired for verbal material is taken as evidence against a material specific deficit during this verbal episodic memory task. Although previous data suggest that left patients are considerably more impaired during some verbal tasks, this may not be specific to the material, but rather the combination of material and task demands. Implications for the material specific hypothesis are discussed.