scholarly journals Temporal Properties of Posterior Parietal Neuron Discharges During Working Memory and Passive Viewing

2007 ◽  
Vol 97 (3) ◽  
pp. 2254-2266 ◽  
Author(s):  
Frederik C. Joelving ◽  
Albert Compte ◽  
Christos Constantinidis
Keyword(s):  
Working Memory ◽  
Posterior Parietal Cortex ◽  
Memory Task ◽  
Power Spectra ◽  
Low Frequency ◽  
Spatial Location ◽  
Spike Trains ◽  
Memory Condition ◽  
Temporal Properties ◽  
Posterior Parietal

Working memory is mediated by the discharges of neurons in a distributed network of brain areas. It was recently suggested that enhanced rhythmicity in neuronal activity may be critical for sustaining remembered information. To test whether working memory is characterized by unique temporal discharge patterns, we analyzed the autocorrelograms and power spectra of spike trains recorded from the posterior parietal cortex of monkeys performing a visuospatial working-memory task. We compared the intervals of active memory maintenance and fixation and repeated the same analysis in spike trains from monkeys never trained to perform any kind of memory task. The most salient effect we observed was a decrease of power in the 5- to 10-Hz frequency range during the presentation of visual stimuli. This pattern was observed both in the working-memory condition and the control condition, although it was more prominent in the former, where it persisted after cue presentation when the monkeys actively remembered the spatial location of the stimulus. Low-frequency power suppression resulted from relative refractory periods that were significantly longer in the working-memory condition and presumably emerged from local-circuit inhibition. We also detected a spectral peak in the 15- to 20-Hz range, although this was more prominent during fixation than during the stimulus and working-memory periods. Our results are in line with previous reports in prefrontal cortex and indicate that unique temporal patterns of single-neuron firing characterize persistent delay activity, although these do not involve the appearance of enhanced oscillations.

scholarly journals Neurons with inverted tuning during the delay periods of working memory tasks in the dorsal prefrontal and posterior parietal cortex

2012 ◽  
Vol 108 (1) ◽  
pp. 31-38 ◽  
Author(s):  
Xin Zhou ◽  
Fumi Katsuki ◽  
Xue-Lian Qi ◽  
Christos Constantinidis
Keyword(s):  
Working Memory ◽  
Prefrontal Cortex ◽  
Parietal Cortex ◽  
Posterior Parietal Cortex ◽  
Memory Task ◽  
Functional Difference ◽  
Initial Stimulus ◽  
Cortical Afferents ◽  
Dorsolateral Prefrontal ◽  
Posterior Parietal

The dorsolateral prefrontal and posterior parietal cortices are two interconnected brain areas that are coactivated in tasks involving functions such as spatial attention and working memory. The response properties of neurons in the two areas are in many respects indistinguishable, yet only prefrontal neurons are able to resist interference by distracting stimuli when subjects are required to remember an initial stimulus. Several mechanisms have been proposed that could account for this functional difference, including the existence of specialized interneuron types, specific to the prefrontal cortex. Although such neurons with inverted tuning during the delay period of a working memory task have been described in the prefrontal cortex, no comparative data exist from other cortical areas that would establish a unique prefrontal role. To test this hypothesis, we analyzed a large database of recordings obtained in the dorsolateral prefrontal and posterior parietal cortex of the same monkeys as they performed working memory tasks. We found that in the prefrontal cortex, neurons with inverted tuning were more numerous and manifested unique properties. Our results give credence to the idea that a division of labor exists between separate neuron types in the prefrontal cortex and that this represents a functional specialization that is not present in its cortical afferents.

scholarly journals Posterior parietal cortex represents sensory history and mediates its effects on behavior

2017 ◽  
Author(s):  
Athena Akrami ◽  
Charles D. Kopec ◽  
Mathew E. Diamond ◽  
Carlos Brody
Keyword(s):  
Working Memory ◽  
Parietal Cortex ◽  
Posterior Parietal Cortex ◽  
Memory Task ◽  
Sensory Stimulus ◽  
Central Component ◽  
Neural Firing ◽  
Sensory Stimuli ◽  
Sensory History ◽  
Posterior Parietal

Many models of cognition and of neural computations posit the use and estimation of prior stimulus statistics1–4: it has long been known that working memory and perception are strongly impacted by previous sensory experience, even when that sensory history is irrelevant for the current task at hand. Nevertheless, the neural mechanisms and brain regions necessary for computing and using such priors are unknown. Here we report that the posterior parietal cortex (PPC) is a critical locus for the representation and use of prior stimulus information. We trained rats in an auditory Parametric Working Memory (PWM) task, and found that rats displayed substantial and readily quantifiable behavioral effects of sensory stimulus history, similar to those observed in humans5,6 and monkeys7. Earlier proposals that PPC supports working memory8,9 predict that optogenetic silencing of this region would impair behavior in our working memory task. Contrary to this prediction, silencing PPC significantly improved performance. Quantitative analyses of behavior revealed that this improvement was due to the selective reduction of the effects of prior sensory stimuli. Electrophysiological recordings showed that PPC neurons carried far more information about sensory stimuli of previous trials than about stimuli of the current trial. Furthermore, the more information about previous trial sensory history in the neural firing rates of a given rat’s PPC, the greater the behavioral effect of sensory history in that rat, suggesting a tight link between behavior and PPC representations of stimulus history. Our results indicate that the PPC is a central component in the processing of sensory stimulus history, and open a window for neurobiological investigation of long-standing questions regarding how perception and working memory are affected by prior sensory information.

Verbal and spatial working memory performance among HIV-infected adults

2002 ◽  
Vol 8 (4) ◽  
pp. 532-538 ◽  
Author(s):  
CHARLES H. HINKIN ◽  
DAVID J. HARDY ◽  
KAREN I. MASON ◽  
STEVEN A. CASTELLON ◽  
MONA N. LAM ◽  
...  
Keyword(s):  
Working Memory ◽  
Mixed Model ◽  
Spatial Working Memory ◽  
Memory Performance ◽  
Memory Task ◽  
Executive Dysfunction ◽  
Spatial Location ◽  
Verbal Working Memory ◽  
Memory Condition ◽  
Percent Accuracy

Subtypes of working memory performance were examined in a cohort of 50 HIV-infected adults and 23 uninfected controls using an n-back paradigm (2-back) in which alphabetic stimuli were quasi-randomly presented to a quadrant of a computer monitor. In the verbal working memory condition, participants determined whether each successive letter matched the letter that appeared two previously in the series, regardless of spatial location. In the spatial working memory condition, participants determined whether each letter matched the spatial location of the letter that had appeared two previously, regardless of letter identity. The dependent variable was percent accuracy in each condition. Results of mixed model ANOVA revealed that the HIV-infected participants performed significantly worse than controls on both the verbal and spatial working memory tasks. A significant main effect for working memory condition was also present with both participant groups performing better on the spatial working memory task. These results, the first study of HIV-infected adults to directly compare verbal versus spatial working memory performance using the identical test stimuli across task conditions, suggests that HIV infection is associated with a decrement in working memory efficiency that is equally apparent for both verbal and spatial processing. These findings implicate central executive dysfunction as a likely substrate and provide the basis for hypothesizing that decline in working memory may contribute to other HIV-associated neuropsychological deficits. (JINS, 2002, 8, 532–538.)

scholarly journals Cerebral cortex activation during the Sternberg verbal working memory task

2020 ◽  
pp. 40-48
Author(s):  
I.S. Bakulin ◽  
A.H. Zabirova ◽  
P.N. Kopnin ◽  
D.O. Sinitsyn ◽  
A.G. Poydasheva ◽  
...  
Keyword(s):  
Working Memory ◽  
Parietal Cortex ◽  
Posterior Parietal Cortex ◽  
Temporal Dynamics ◽  
Memory Task ◽  
Occipital Cortex ◽  
Dorsolateral Prefrontal ◽  
Posterior Parietal ◽  
Sternberg Task

Despite intensive study, the data regarding functional role of specific brain regions in the working memory processes still remain controversial. The study was aimed to determine the activation of cerebral cortex regions at different stages of the working memory task (information encoding, maintenance and retrieval). Functional magnetic resonance imaging (fMRI) with the modified Sternberg task was applied to 19 healthy volunteers. The objective of the task was to memorize and retain in memory the sequence of 7 letters with the subsequent comparison of one letter with the sequence. Activation was analyzed during three periods of the task compared to the rest period, as well as temporal dynamics of changes in BOLD signal intensity in three regions: left dorsolateral prefrontal, left posterior parietal and left occipital cortex. According to the results, significant activation of the regions in prefrontal and posterior parietal cortex was observed during all periods of the task (p < 0.05), but there were changes in its localization and lateralization. The activation pattern during the maintenance period corresponded to the fronto-parietal control network components. According to the analysis of temporal dynamics of changes in BOLD signal intensity, the most prominent activation of the dorsolateral prefrontal cortex and parietal cortex was observed in the end of the encoding period, during the maintenance period and in the beginning of the retrieval period, which confirmed the role of those areas in the working memory processes. The maximum of occipital cortex activation was observed during encoding period. The study confirmed the functional role of the dorsolateral prefrontal cortex and posterior parietal cortex in the working memory mechanisms during all stages of the Sternberg task.

scholarly journals Lower neuronal variability in the monkey dorsolateral prefrontal than posterior parietal cortex

2015 ◽  
Vol 114 (4) ◽  
pp. 2194-2203 ◽  
Author(s):  
Xue-Lian Qi ◽  
Christos Constantinidis
Keyword(s):  
Working Memory ◽  
Firing Rate ◽  
Parietal Cortex ◽  
Posterior Parietal Cortex ◽  
Memory Task ◽  
Fano Factor ◽  
Functional Differentiation ◽  
Neuronal Responses ◽  
Dorsolateral Prefrontal ◽  
Posterior Parietal

The dorsolateral prefrontal and posterior parietal cortex are two brain areas involved in cognitive functions such as spatial attention and working memory. When tested with identical tasks, only subtle differences in firing rate are present between neurons recorded in the two areas. In this article we report that major differences in neuronal variability characterize the two areas during working memory. The Fano factors of spike counts in dorsolateral prefrontal neurons were consistently lower than those of the posterior parietal cortex across a range of tasks, epochs, and conditions in the same monkeys. Variability differences were observed despite minor differences in firing rates between the two areas in the tasks tested and higher overall firing rate in the prefrontal than in the posterior parietal sample. Other measures of neuronal discharge variability, such as the coefficient of variation of the interspike interval, displayed the same pattern of lower prefrontal variability. Fano factor values were negatively correlated with performance in the working memory task, suggesting that higher neuronal variability was associated with diminished task performance. The results indicate that information involving remembered stimuli is more reliably represented in the prefrontal than the posterior parietal cortex based on the variability of neuronal responses, and suggest functional differentiation between the two areas beyond differences in firing rate.

Effects of High-Definition Transcranial Direct Current Stimulation and Theta Burst Stimulation for Modulating the Posterior Parietal Cortex

2019 ◽  
Vol 25 (09) ◽  
pp. 972-984
Author(s):  
Tian Gan ◽  
Stevan Nikolin ◽  
Colleen K. Loo ◽  
Donel M. Martin
Keyword(s):  
Working Memory ◽  
Parietal Cortex ◽  
Direct Current ◽  
Posterior Parietal Cortex ◽  
Theta Burst Stimulation ◽  
Burst Stimulation ◽  
High Definition ◽  
Attention Task ◽  
Posterior Parietal ◽  
Theta Burst

AbstractObjectives:Noninvasive brain stimulation methods, including high-definition transcranial direct current stimulation (HD-tDCS) and theta burst stimulation (TBS) have emerged as novel tools to modulate and explore brain function. However, the relative efficacy of these newer stimulation approaches for modulating cognitive functioning remains unclear. This study investigated the cognitive effects of HD-tDCS, intermittent TBS (iTBS) and prolonged continuous TBS (ProcTBS) and explored the potential of these approaches for modulating hypothesized functions of the left posterior parietal cortex (PPC).Methods:Twenty-two healthy volunteers attended four experimental sessions in a cross-over experimental design. In each session, participants either received HD-tDCS, iTBS, ProcTBS or sham, and completed cognitive tasks, including a divided attention task, a working memory maintenance task and an attention task (emotional Stroop test).Results:The results showed that compared to sham, HD-tDCS, iTBS and ProcTBS caused significantly faster response times on the emotional Stroop task. The effect size (Cohen’sd) wasd= .32 for iTBS (p&lt; .001), .21 for ProcTBS (p= .01) and .15 for HD-tDCS (p= .044). However, for the performance on the divided attention and working memory maintenance tasks, no significant effect of stimulation was found.Conclusions:The results suggest that repetitive transcranial magnetic stimulation techniques, including TBS, may have greater efficacy for modulating cognition compared with HD-tDCS, and extend existing knowledge about specific functions of the left PPC.

scholarly journals Dance and emotion in posterior parietal cortex: A low-frequency rTMS study

2012 ◽  
Vol 5 (2) ◽  
pp. 130-136 ◽  
Author(s):  
Marie-Hélène Grosbras ◽  
Haodan Tan ◽  
Frank Pollick
Keyword(s):  
Parietal Cortex ◽  
Posterior Parietal Cortex ◽  
Low Frequency ◽  
Posterior Parietal ◽  
Low Frequency Rtms
Sign in / Sign up

Export Citation Format

Share Document