The eye movement measure of memory and its relationship with explicit measures

The Effect of Body Expressions on the Learning Process and Facial Recognition among Healthy Participants and Individuals with Traumatic Brain Injury: Examination Using Eye Movements

OBJECTIVE

Context-dependent effect (CDE) is a process by which reinstating at test the original learning context enhances the recall ability of the material being studied. Although recognition by people with traumatic brain injury (TBI) is poorer than that of healthy controls, both groups show CDE equally. In the current study, we seek to test the effect of body emotional expressions as contextual information, on facial recognition, and eye movements.

METHOD

Twenty-four healthy individuals and 27 patients with moderate-to-severe TBI participated in the study. Participants were exposed to photos of people with neutral facial and body expressions and were asked to remember the people for a subsequent memory test. In the testing session, they were asked to determine whether the person presented to them had appeared before, under two conditions: (1) where the context remains constant (facial and body expressions remained neutral-Repeat condition) and (2) where the context changes (facial expression remained neutral but the body expression changed to angry or happy-Re-pair condition).

RESULTS

While the memory of the individuals with TBI was poorer than that of the controls, both groups exhibited equal CDE. We found that both groups, controls more than TBI, spent most of their time looking at the head. Furthermore, longer dwell time was associated with better recognition in the study phase.

CONCLUSIONS

These findings are consistent with previous studies showing that despite impaired memory following TBI compared to a control group, CDE was preserved. The current study extends the context effect to body postures that express emotion.

Eye movements support the link between conscious memory and medial temporal lobe function

When individuals select the recently studied (and familiar) item in a multiple-choice memory test, they direct a greater proportion of viewing time toward the to-be-selected item when their choice is correct than when their choice is incorrect. Thus, for both correct and incorrect choices, individuals indicate that the chosen item is old, but viewing time nevertheless distinguishes between old and new items. What kind of memory supports this preferential viewing effect? We recorded eye movements while participants made three-alternative, forced-choice recognition memory judgments for scenes. In experiment 1 (n = 30), the magnitude of the preferential viewing effect was strongly correlated with measures of conscious, declarative memory: recognition accuracy as well as the difference in confidence ratings and in response times for correct and incorrect choices. In four analyses that minimized the contribution of declarative memory in order to detect a possible contribution from other processes, the preferential viewing effect was absent. In experiment 2, five memory-impaired patients with medial temporal lobe lesions exhibited a diminished preferential viewing effect. These patients also exhibited poor recognition accuracy and reduced differences in confidence ratings and response times for correct and incorrect choices. We propose that the preferential viewing effect is a phenomenon of conscious, declarative memory and is dependent on the medial temporal lobe. The findings support the link between medial temporal lobe function and declarative memory. When the effects of experience depend on the medial temporal lobe, the effects reflect conscious memory.

When eye movements express memory for old and new scenes in the absence of awareness and independent of hippocampus

Eye movements can reflect memory. For example, participants make fewer fixations and sample fewer regions when viewing old versus new scenes (the repetition effect). It is unclear whether the repetition effect requires that participants have knowledge (awareness) of the old–new status of the scenes or if it can occur independent of knowledge about old–new status. It is also unclear whether the repetition effect is hippocampus-dependent or hippocampus-independent. A complication is that testing conscious memory for the scenes might interfere with the expression of unconscious (unaware), experience-dependent eye movements. In experiment 1, 75 volunteers freely viewed old and new scenes without knowledge that memory for the scenes would later be tested. Participants then made memory judgments and confidence judgments for each scene during a surprise recognition memory test. Participants exhibited the repetition effect regardless of the accuracy or confidence associated with their memory judgments (i.e., the repetition effect was independent of their awareness of the old–new status of each scene). In experiment 2, five memory-impaired patients with medial temporal lobe damage and six controls also viewed old and new scenes without expectation of memory testing. Both groups exhibited the repetition effect, even though the patients were impaired at recognizing which scenes were old and which were new. Thus, when participants viewed scenes without expectation of memory testing, eye movements associated with old and new scenes reflected unconscious, hippocampus-independent memory. These findings are consistent with the formulation that, when memory is expressed independent of awareness, memory is hippocampus-independent.