Normative data for measuring performance change on parallel forms of a 15-word list recall test.

Declarative memory evaluation is an essential step in the clinical and neuropsychological assessment of a variety of neurological disorders. It typically addresses the issue of normality/abnormality of an individual's performance. Another clinical application of the neuropsychological assessment of declarative memory is the longitudinal evaluation of an individual's performance change. In fact, in a variety of neurological conditions repeated assessments are needed to evaluate the modifications of a memory disorder as a function of time or in response to a pharmacological or rehabilitation treatment. This study was aimed at collecting data for measuring and interpreting performance change on a memory test for verbal material. For this purpose, we administered to 100 healthy subjects (age range 20-80 years; years of formal education range 8-17 years) three parallel forms of a test requiring the immediate and delayed recall of a 15-word list. The subjects performed the recall test three times (each time with a different list) at least 1 week apart. The order of the lists was randomized across subjects. Results revealed that performance on the three lists was highly correlated and did not vary as a function of the order of presentation. However, accuracy of recall was slightly better on a list compared to the others. Based on a method devised by Payne and Jones (J Clin Psychol 13:115-121, 1957), we provide normative data for establishing whether a discrepancy in recall accuracy on two versions of the test exceeds the discrepancy expected based on the performance of normal controls.

Activity of hippocampal, amygdala, and neocortex during the Rey auditory verbal learning test: an event-related potential study in epileptic patients.

OBJECTIVE: Previous evidence in epileptic subjects has shown that theta (about 4-7Hz) and gamma rhythms (about 40-45Hz) of hippocampus, amygdala, and neocortex were temporally synchronized during the listening of repeated words successfully remembered (Babiloni et al., 2009). Here we re-analyzed those electroencephalographic (EEG) data to test whether a parallel increase in amplitude of late positive event-related potentials takes place. METHODS: Intracerebral electroencephalographic (EEG) activity had been recorded in five subjects with drug-resistant temporal lobe epilepsy, undergoing pre-surgical evaluation. During the recording of the intracerebral EEG activity, the subjects performed a computerized version of the Rey auditory verbal learning test (RAVLT). They heard the same list of 15 common words for five times. Each time, immediately after the listening of the list, the subjects were required to repeat as many words as they could recall. RESULTS: We found that late positive event-related potentials (ERPs) peaking at about 350ms post-stimulus in amygdala, hippocampus, and occipital-temporal cortex had a higher amplitude during the listening of the repeated words that were subsequently recalled than for those that were not recalled. CONCLUSIONS: Late positive ERPs reflect a functional mechanism implemented in a human brain network spanning amygdala, hippocampus, and occipital-temporal cortex which is at the basis of the memorization processes of verbal materials. SIGNIFICANCE: This ERP component is a promising neuromarker of successful memorization of repeated words in humans.

Hippocampal, amygdala, and neocortical synchronization of theta rhythms is related to an immediate recall during rey auditory verbal learning test.

It is well known that theta rhythms (3-8 Hz) are the fingerprint of hippocampus, and that neural activity accompanying encoding of words differs according to whether the items are later remembered or forgotten ["subsequent memory effect" (SME)]. Here, we tested the hypothesis that temporal synchronization of theta rhythms among hippocampus, amygdala, and neocortex is related to immediate memorization of repeated words. To address this issue, intracerebral electroencephalographic (EEG) activity was recorded in five subjects with drug-resistant temporal lobe epilepsy (TLE), under presurgical monitoring routine. During the recording of the intracerebral EEG activity, the subjects performed a computerized version of Rey auditory verbal learning test (RAVLT), a popular test for the clinical evaluation of the immediate and delayed memory. They heard the same list of 15 common words for five times. Each time, immediately after listening the list, the subjects were required to repeat as many words as they could recall. Spectral coherence of the intracerebral EEG activity was computed in order to assess the temporal synchronization of the theta (about 3-8 Hz) rhythms among hippocampus, amygdala, and temporal-occipital neocortex. We found that theta coherence values between amygdala and hippocampus, and between hippocampus and occipital-temporal cortex, were higher in amplitude during successful than unsuccessful immediate recall. A control analysis showed that this was true also for a gamma band (40-45 Hz). Furthermore, these theta and gamma effects were not observed in an additional (control) subject with drug-resistant TLE and a wide lesion to hippocampus. In conclusion, a successful immediate recall to the RAVLT was associated to the enhancement of temporal synchronization of the theta (gamma) rhythms within a cerebral network including hippocampus, amygdala, and temporal-occipital neocortex.