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Recency Effects in the Inferior Parietal Lobe during Verbal Recognition Memory.

Buchsbaum BR, Ye D, D'Esposito M - Front Hum Neurosci (2011)

Bottom Line: A key question regarding recency effects in the LIPC is whether they fundamentally reflect the storage (and strength) of information in memory, or whether such effects are a consequence of task difficulty or an upswing in resting state network activity.Using functional magnetic resonance imaging we show that recency effects in the LIPC are independent of the difficulty of recognition memory decisions, that they are not a by-product of an increase in resting state network activity, and that they appear to dissociate from regions known to be involved in verbal working memory maintenance.We conclude with a discussion of two alternative explanations - the memory strength and "expectancy" hypotheses, respectively - of the parietal lobe recency effect.

View Article: PubMed Central - PubMed

Affiliation: Rotman Research Institute, Baycrest Hospital Toronto, ON, Canada.

ABSTRACT
The most recently encountered information is often most easily remembered in psychological tests of memory. Recent investigations of the neural basis of such "recency effects" have shown that activation in the lateral inferior parietal cortex (LIPC) tracks the recency of a probe item when subjects make recognition memory judgments. A key question regarding recency effects in the LIPC is whether they fundamentally reflect the storage (and strength) of information in memory, or whether such effects are a consequence of task difficulty or an upswing in resting state network activity. Using functional magnetic resonance imaging we show that recency effects in the LIPC are independent of the difficulty of recognition memory decisions, that they are not a by-product of an increase in resting state network activity, and that they appear to dissociate from regions known to be involved in verbal working memory maintenance. We conclude with a discussion of two alternative explanations - the memory strength and "expectancy" hypotheses, respectively - of the parietal lobe recency effect.

No MeSH data available.


Illustration of the dual-modality continuous recognition task. Each level represents either the auditory or visual stream as labeled. Each box represents a stimulus presented in either the auditory or visual modality. Stimuli were presented for 2.5-s with an intertrial interval (ITI) between 800 and 1200 ms, with a mean ITI of 1000 ms. Repetition occurred across modality as auditory repetitions (AR) between the auditory stream and the visual stream or as visual repetitions (VR) within the visual modality. Repetition intervals of AR and VR trials varied between five levels, from 1 to 16 (1, 2, 4, 8, and 16). Repetition modality was crossed with repetition interval to yield 10 distinct repetition conditions.
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Figure 1: Illustration of the dual-modality continuous recognition task. Each level represents either the auditory or visual stream as labeled. Each box represents a stimulus presented in either the auditory or visual modality. Stimuli were presented for 2.5-s with an intertrial interval (ITI) between 800 and 1200 ms, with a mean ITI of 1000 ms. Repetition occurred across modality as auditory repetitions (AR) between the auditory stream and the visual stream or as visual repetitions (VR) within the visual modality. Repetition intervals of AR and VR trials varied between five levels, from 1 to 16 (1, 2, 4, 8, and 16). Repetition modality was crossed with repetition interval to yield 10 distinct repetition conditions.

Mentions: The goal of the present study is to test whether recency effects in the LIPC persist even in the case where lag and difficulty are no longer strictly confounded. To achieve this decoupling between item lag and item difficulty in recognition memory, we adopted a paradigm that involved the presentation of two continuous streams of words – one in the visual modality, the relevant stream – and one in the auditory modality, the irrelevant stream. Words from the relevant stream are sometimes repeated in the visual stream but subjects nevertheless have to classify those items as “new” (see Figure 1). As we knew from a behavioral pilot study, accuracy in rejecting these “lure” probes (i.e., probes that had previously appeared only in the unattended stream) does not strictly decrease as a function of lag as is seen for items that repeat in the attended stream. Thus, by examining the pattern of responses as a function of lag for both visual repetitions (VRs) and lures, we can examine the extent to which recency-related activation in LIPC is dissociable from item difficulty. If we find that activity in LIPC tracks the performance profile across lag for relevant and irrelevant items, we may conclude that the effect is indeed a trivial consequence of task difficulty. On the contrary, if activity in LIPC is monotonically related to recency in both conditions, the evidence will rather support a genuine link between LIPC activity and mnemonic recency as we have previously hypothesized (Buchsbaum et al., 2011b).


Recency Effects in the Inferior Parietal Lobe during Verbal Recognition Memory.

Buchsbaum BR, Ye D, D'Esposito M - Front Hum Neurosci (2011)

Illustration of the dual-modality continuous recognition task. Each level represents either the auditory or visual stream as labeled. Each box represents a stimulus presented in either the auditory or visual modality. Stimuli were presented for 2.5-s with an intertrial interval (ITI) between 800 and 1200 ms, with a mean ITI of 1000 ms. Repetition occurred across modality as auditory repetitions (AR) between the auditory stream and the visual stream or as visual repetitions (VR) within the visual modality. Repetition intervals of AR and VR trials varied between five levels, from 1 to 16 (1, 2, 4, 8, and 16). Repetition modality was crossed with repetition interval to yield 10 distinct repetition conditions.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3139920&req=5

Figure 1: Illustration of the dual-modality continuous recognition task. Each level represents either the auditory or visual stream as labeled. Each box represents a stimulus presented in either the auditory or visual modality. Stimuli were presented for 2.5-s with an intertrial interval (ITI) between 800 and 1200 ms, with a mean ITI of 1000 ms. Repetition occurred across modality as auditory repetitions (AR) between the auditory stream and the visual stream or as visual repetitions (VR) within the visual modality. Repetition intervals of AR and VR trials varied between five levels, from 1 to 16 (1, 2, 4, 8, and 16). Repetition modality was crossed with repetition interval to yield 10 distinct repetition conditions.
Mentions: The goal of the present study is to test whether recency effects in the LIPC persist even in the case where lag and difficulty are no longer strictly confounded. To achieve this decoupling between item lag and item difficulty in recognition memory, we adopted a paradigm that involved the presentation of two continuous streams of words – one in the visual modality, the relevant stream – and one in the auditory modality, the irrelevant stream. Words from the relevant stream are sometimes repeated in the visual stream but subjects nevertheless have to classify those items as “new” (see Figure 1). As we knew from a behavioral pilot study, accuracy in rejecting these “lure” probes (i.e., probes that had previously appeared only in the unattended stream) does not strictly decrease as a function of lag as is seen for items that repeat in the attended stream. Thus, by examining the pattern of responses as a function of lag for both visual repetitions (VRs) and lures, we can examine the extent to which recency-related activation in LIPC is dissociable from item difficulty. If we find that activity in LIPC tracks the performance profile across lag for relevant and irrelevant items, we may conclude that the effect is indeed a trivial consequence of task difficulty. On the contrary, if activity in LIPC is monotonically related to recency in both conditions, the evidence will rather support a genuine link between LIPC activity and mnemonic recency as we have previously hypothesized (Buchsbaum et al., 2011b).

Bottom Line: A key question regarding recency effects in the LIPC is whether they fundamentally reflect the storage (and strength) of information in memory, or whether such effects are a consequence of task difficulty or an upswing in resting state network activity.Using functional magnetic resonance imaging we show that recency effects in the LIPC are independent of the difficulty of recognition memory decisions, that they are not a by-product of an increase in resting state network activity, and that they appear to dissociate from regions known to be involved in verbal working memory maintenance.We conclude with a discussion of two alternative explanations - the memory strength and "expectancy" hypotheses, respectively - of the parietal lobe recency effect.

View Article: PubMed Central - PubMed

Affiliation: Rotman Research Institute, Baycrest Hospital Toronto, ON, Canada.

ABSTRACT
The most recently encountered information is often most easily remembered in psychological tests of memory. Recent investigations of the neural basis of such "recency effects" have shown that activation in the lateral inferior parietal cortex (LIPC) tracks the recency of a probe item when subjects make recognition memory judgments. A key question regarding recency effects in the LIPC is whether they fundamentally reflect the storage (and strength) of information in memory, or whether such effects are a consequence of task difficulty or an upswing in resting state network activity. Using functional magnetic resonance imaging we show that recency effects in the LIPC are independent of the difficulty of recognition memory decisions, that they are not a by-product of an increase in resting state network activity, and that they appear to dissociate from regions known to be involved in verbal working memory maintenance. We conclude with a discussion of two alternative explanations - the memory strength and "expectancy" hypotheses, respectively - of the parietal lobe recency effect.

No MeSH data available.