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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.


Mean level of activation as a function of lag and source modality in selected regions of interest (1–7). 1. Left dorsolateral prefrontal cortex. 2. Left intra parietal sulcus. 3. Left anterior insula. 4. Left inferior parietal lobe. 5. Right dorsolateral prefrontal cortex. 6. Right inferior parietal lobe. 7. Right anterior insula.
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Figure 4: Mean level of activation as a function of lag and source modality in selected regions of interest (1–7). 1. Left dorsolateral prefrontal cortex. 2. Left intra parietal sulcus. 3. Left anterior insula. 4. Left inferior parietal lobe. 5. Right dorsolateral prefrontal cortex. 6. Right inferior parietal lobe. 7. Right anterior insula.

Mentions: To examine the precise pattern of effects in several of the regions showing either lag × repetition modality interaction or in the conjunction of (negative) linear trends across lag (ARlinear ∩ VRlinear), we extracted the top eight contiguous voxels surrounding the coordinate of maximal activation in the relevant group contrast map (Figure 4). These ROIs were then used to select voxels from the individual t-statistic contrast maps in each subject and for all of the experimental conditions (e.g., all combinations of lag and repetition modality – 2 × 5 = 10 conditions). The mean value for each condition was then computed (Masson and Loftus, 2003) and plotted with standard errors for each ROI in Figure 4. The purpose of this ROI extraction was not for hypothesis-testing but rather to show the shape of parametric effect of lag across as a function of repetition modality. Five ROIs – bilateral MFG, bilateral anterior insula, and the left IPS – were selected from the lag × source modality group level interaction map, while two ROIs (bilateral LIPC) were taken from the lag conjunction analysis (negative linear effect of lag; ARlinear ∩ VRlinear). As one can see from Figure 4, there is a similar pattern of effects for the interaction ROIs, where there is a negative trend (flattening out at about lag 8) for the AR condition and nearly a inverted effect for the VR condition – except that in the VR conditions, activation changes more precipitously, flattening out in its upward course as early as lag 2 for the MFG and IPS ROIs. In contrast, LIPC activation patterns for the VR and AR conditions have the same general form, with maximal activity at lag 1, which flattens out at approximately lag 4 or 8. In summary, the ROI plots show that while the bilateral LIPC region tracks recency independent of whether the probe is a hit (VR) or a lure (AR), the anterior insula, IPS, and MFG show an effect whereby the pattern of activity as a function of lag sharply diverges depending on the status of the memory probe.


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

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

Mean level of activation as a function of lag and source modality in selected regions of interest (1–7). 1. Left dorsolateral prefrontal cortex. 2. Left intra parietal sulcus. 3. Left anterior insula. 4. Left inferior parietal lobe. 5. Right dorsolateral prefrontal cortex. 6. Right inferior parietal lobe. 7. Right anterior insula.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

Figure 4: Mean level of activation as a function of lag and source modality in selected regions of interest (1–7). 1. Left dorsolateral prefrontal cortex. 2. Left intra parietal sulcus. 3. Left anterior insula. 4. Left inferior parietal lobe. 5. Right dorsolateral prefrontal cortex. 6. Right inferior parietal lobe. 7. Right anterior insula.
Mentions: To examine the precise pattern of effects in several of the regions showing either lag × repetition modality interaction or in the conjunction of (negative) linear trends across lag (ARlinear ∩ VRlinear), we extracted the top eight contiguous voxels surrounding the coordinate of maximal activation in the relevant group contrast map (Figure 4). These ROIs were then used to select voxels from the individual t-statistic contrast maps in each subject and for all of the experimental conditions (e.g., all combinations of lag and repetition modality – 2 × 5 = 10 conditions). The mean value for each condition was then computed (Masson and Loftus, 2003) and plotted with standard errors for each ROI in Figure 4. The purpose of this ROI extraction was not for hypothesis-testing but rather to show the shape of parametric effect of lag across as a function of repetition modality. Five ROIs – bilateral MFG, bilateral anterior insula, and the left IPS – were selected from the lag × source modality group level interaction map, while two ROIs (bilateral LIPC) were taken from the lag conjunction analysis (negative linear effect of lag; ARlinear ∩ VRlinear). As one can see from Figure 4, there is a similar pattern of effects for the interaction ROIs, where there is a negative trend (flattening out at about lag 8) for the AR condition and nearly a inverted effect for the VR condition – except that in the VR conditions, activation changes more precipitously, flattening out in its upward course as early as lag 2 for the MFG and IPS ROIs. In contrast, LIPC activation patterns for the VR and AR conditions have the same general form, with maximal activity at lag 1, which flattens out at approximately lag 4 or 8. In summary, the ROI plots show that while the bilateral LIPC region tracks recency independent of whether the probe is a hit (VR) or a lure (AR), the anterior insula, IPS, and MFG show an effect whereby the pattern of activity as a function of lag sharply diverges depending on the status of the memory probe.

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.