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Functional specialization of the left ventral parietal cortex in working memory.

Langel J, Hakun J, Zhu DC, Ravizza SM - Front Hum Neurosci (2014)

Bottom Line: An anterior region of the VPC was bilaterally active during novel targets in the oddball task and during retrieval in WM, while more posterior regions of the VPC displayed dissociable functions in the left and right hemisphere, with the left being active during the encoding and retrieval of WM, but not during the oddball task and the right showing the reverse pattern.These results suggest that bilateral regions of the anterior VPC subserve non-mnemonic processes, such as stimulus-driven attention during WM retrieval and oddball detection.The left posterior VPC may be important for speech-related processing important for both working memory and perception, while the right hemisphere is more lateralized for attention.

View Article: PubMed Central - PubMed

Affiliation: Neuroscience Program, Michigan State University East Lansing, MI, USA.

ABSTRACT
The function of the ventral parietal cortex (VPC) is subject to much debate. Many studies suggest a lateralization of function in the VPC, with the left hemisphere facilitating verbal working memory and the right subserving stimulus-driven attention. However, many attentional tasks elicit activity in the VPC bilaterally. To elucidate the potential divides across the VPC in function, we assessed the pattern of activity in the VPC bilaterally across two tasks that require different demands, an oddball attentional task with low working memory demands and a working memory task. An anterior region of the VPC was bilaterally active during novel targets in the oddball task and during retrieval in WM, while more posterior regions of the VPC displayed dissociable functions in the left and right hemisphere, with the left being active during the encoding and retrieval of WM, but not during the oddball task and the right showing the reverse pattern. These results suggest that bilateral regions of the anterior VPC subserve non-mnemonic processes, such as stimulus-driven attention during WM retrieval and oddball detection. The left posterior VPC may be important for speech-related processing important for both working memory and perception, while the right hemisphere is more lateralized for attention.

No MeSH data available.


Experimental design of the oddball (A) and working memory [WM; (B)] task. The oddball task consisted of novel targets (Korean and English letters), non-targets (percentage signs) and control targets (same as non-targets, but used as the baseline condition for comparison purposes; one-third of the time the percentage signs were denoted as the control targets); stimulus duration was 600 ms, while the interstimulus interval was 600 ms. (A). Presented is an example sequence of a novel target (Korean letter) followed by a series of standard stimuli (%) and another novel target (English letter). Participants indicated whenever they saw a stimulus that was not a percentage sign. The WM task consisted of verbal (English letters only) and object (Korean letters only) trials. Presented is a verbal trial followed by a correctly ordered probe (B). A fixation cross marked the onset of each trial (2 s), followed by the presentation of five randomly selected stimuli (all verbal or all object; 8 s). Participants were to rehearse the stimuli in serial order (16 s) and make a response when the probe (r→c) was presented (4 s). A fixation cross marked the end of the trial (12 s).
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Figure 1: Experimental design of the oddball (A) and working memory [WM; (B)] task. The oddball task consisted of novel targets (Korean and English letters), non-targets (percentage signs) and control targets (same as non-targets, but used as the baseline condition for comparison purposes; one-third of the time the percentage signs were denoted as the control targets); stimulus duration was 600 ms, while the interstimulus interval was 600 ms. (A). Presented is an example sequence of a novel target (Korean letter) followed by a series of standard stimuli (%) and another novel target (English letter). Participants indicated whenever they saw a stimulus that was not a percentage sign. The WM task consisted of verbal (English letters only) and object (Korean letters only) trials. Presented is a verbal trial followed by a correctly ordered probe (B). A fixation cross marked the onset of each trial (2 s), followed by the presentation of five randomly selected stimuli (all verbal or all object; 8 s). Participants were to rehearse the stimuli in serial order (16 s) and make a response when the probe (r→c) was presented (4 s). A fixation cross marked the end of the trial (12 s).

Mentions: Behavioral data were collected via the E-prime software package (Psychology Software Tools) with a fiber optic response keypad. For the oddball task, participants were shown a series of percent signs (%) interspersed with novel target stimuli at random times (Figure 1A). Novel targets consisted of English and Korean letters and occurred with a minimum of 14.4 s and a maximum of 25.2 s from the time of the last target. The jitter in the oddball task was set in increments of 1800 ms; specifically, oddball events could occur at one of seven times (14.4, 16.2, 18, 19.8, 21.6, 23.4, or 25.2 s) after the previous oddball target. Participants were asked to press their right index finger on the keypad whenever they saw a stimulus that was not a percentage sign. Stimulus duration was 600 ms and a blank screen was presented for 600 ms between stimuli. A subset of the standard stimuli (percent signs) were used as the baseline condition, so that we could isolate activity to the standard stimulus from that associated with novel targets; this was denoted as the “control target” for the task. These control targets were randomly selected percent signs with the same presentation constraints as the novel targets. The oddball task was completed in five runs (4 min 48 s each) and the total number of trials per condition varied from 15 to 30, since the novel targets were presented at random times. On average, 49.3% of the novel targets were object stimuli, while 50.7% were verbal stimuli.


Functional specialization of the left ventral parietal cortex in working memory.

Langel J, Hakun J, Zhu DC, Ravizza SM - Front Hum Neurosci (2014)

Experimental design of the oddball (A) and working memory [WM; (B)] task. The oddball task consisted of novel targets (Korean and English letters), non-targets (percentage signs) and control targets (same as non-targets, but used as the baseline condition for comparison purposes; one-third of the time the percentage signs were denoted as the control targets); stimulus duration was 600 ms, while the interstimulus interval was 600 ms. (A). Presented is an example sequence of a novel target (Korean letter) followed by a series of standard stimuli (%) and another novel target (English letter). Participants indicated whenever they saw a stimulus that was not a percentage sign. The WM task consisted of verbal (English letters only) and object (Korean letters only) trials. Presented is a verbal trial followed by a correctly ordered probe (B). A fixation cross marked the onset of each trial (2 s), followed by the presentation of five randomly selected stimuli (all verbal or all object; 8 s). Participants were to rehearse the stimuli in serial order (16 s) and make a response when the probe (r→c) was presented (4 s). A fixation cross marked the end of the trial (12 s).
© Copyright Policy - open-access
Related In: Results  -  Collection

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Figure 1: Experimental design of the oddball (A) and working memory [WM; (B)] task. The oddball task consisted of novel targets (Korean and English letters), non-targets (percentage signs) and control targets (same as non-targets, but used as the baseline condition for comparison purposes; one-third of the time the percentage signs were denoted as the control targets); stimulus duration was 600 ms, while the interstimulus interval was 600 ms. (A). Presented is an example sequence of a novel target (Korean letter) followed by a series of standard stimuli (%) and another novel target (English letter). Participants indicated whenever they saw a stimulus that was not a percentage sign. The WM task consisted of verbal (English letters only) and object (Korean letters only) trials. Presented is a verbal trial followed by a correctly ordered probe (B). A fixation cross marked the onset of each trial (2 s), followed by the presentation of five randomly selected stimuli (all verbal or all object; 8 s). Participants were to rehearse the stimuli in serial order (16 s) and make a response when the probe (r→c) was presented (4 s). A fixation cross marked the end of the trial (12 s).
Mentions: Behavioral data were collected via the E-prime software package (Psychology Software Tools) with a fiber optic response keypad. For the oddball task, participants were shown a series of percent signs (%) interspersed with novel target stimuli at random times (Figure 1A). Novel targets consisted of English and Korean letters and occurred with a minimum of 14.4 s and a maximum of 25.2 s from the time of the last target. The jitter in the oddball task was set in increments of 1800 ms; specifically, oddball events could occur at one of seven times (14.4, 16.2, 18, 19.8, 21.6, 23.4, or 25.2 s) after the previous oddball target. Participants were asked to press their right index finger on the keypad whenever they saw a stimulus that was not a percentage sign. Stimulus duration was 600 ms and a blank screen was presented for 600 ms between stimuli. A subset of the standard stimuli (percent signs) were used as the baseline condition, so that we could isolate activity to the standard stimulus from that associated with novel targets; this was denoted as the “control target” for the task. These control targets were randomly selected percent signs with the same presentation constraints as the novel targets. The oddball task was completed in five runs (4 min 48 s each) and the total number of trials per condition varied from 15 to 30, since the novel targets were presented at random times. On average, 49.3% of the novel targets were object stimuli, while 50.7% were verbal stimuli.

Bottom Line: An anterior region of the VPC was bilaterally active during novel targets in the oddball task and during retrieval in WM, while more posterior regions of the VPC displayed dissociable functions in the left and right hemisphere, with the left being active during the encoding and retrieval of WM, but not during the oddball task and the right showing the reverse pattern.These results suggest that bilateral regions of the anterior VPC subserve non-mnemonic processes, such as stimulus-driven attention during WM retrieval and oddball detection.The left posterior VPC may be important for speech-related processing important for both working memory and perception, while the right hemisphere is more lateralized for attention.

View Article: PubMed Central - PubMed

Affiliation: Neuroscience Program, Michigan State University East Lansing, MI, USA.

ABSTRACT
The function of the ventral parietal cortex (VPC) is subject to much debate. Many studies suggest a lateralization of function in the VPC, with the left hemisphere facilitating verbal working memory and the right subserving stimulus-driven attention. However, many attentional tasks elicit activity in the VPC bilaterally. To elucidate the potential divides across the VPC in function, we assessed the pattern of activity in the VPC bilaterally across two tasks that require different demands, an oddball attentional task with low working memory demands and a working memory task. An anterior region of the VPC was bilaterally active during novel targets in the oddball task and during retrieval in WM, while more posterior regions of the VPC displayed dissociable functions in the left and right hemisphere, with the left being active during the encoding and retrieval of WM, but not during the oddball task and the right showing the reverse pattern. These results suggest that bilateral regions of the anterior VPC subserve non-mnemonic processes, such as stimulus-driven attention during WM retrieval and oddball detection. The left posterior VPC may be important for speech-related processing important for both working memory and perception, while the right hemisphere is more lateralized for attention.

No MeSH data available.