Asymmetries in numerical density of pyramidal neurons in the fifth layer of the human posterior parietal cortex

Background/Aim. Both superior parietal lobule (SPL) of dorsolateral hemispheric surface and precuneus (PEC) of medial surface are the parts of posterior parietal cortex. The aim of this study was to determine the numerical density (NV) of pyramidal neurons in the layer V of SPL and PEC and their potential differences. Methods. From 20 (40 hemispheres) formaline fixed human brains (both sexes; 27- 65 years) tissue blocks from SPL and PEC from the left and right hemisphere were used. According to their size the brains were divided into two groups, the group I with the larger left (15 brains) and the group II with the larger right hemisphere (5 brains). Serial Nissl sections (5 ?m) of the left and right SPL and PEC were used for stereological estimation of NV of the layer V pyramidal neurons. Results. NV of pyramidal neurons in the layer V in the left SPL of brains with larger left hemispheres was significantly higher than in the left SPL of brains with larger right hemisphere. Comparing sides in brains with larger left hemisphere, the left SPL had higher NV than the right one, and then the left PEC, and the right SPL had significantly higher NV than the right PEC. Comparing sides in brains with the larger right hemisphere, the left SPL had significantly higher NV than left PEC, but the right SPL had significantly higher NV than left SPL and the right PEC. Conclusion. Generally, there is an inverse relationship of NV between the medial and lateral areas of the human posterior parietal cortex. The obtained values were different between the brains with larger left and right hemispheres, as well as between the SPL and PEC. In all the comparisons the left SPL had the highest values of NV of pyramidal neurons in the layer V (4771.80 mm-3), except in brains with the larger right hemisphere.

Download Full-text

Saccades, attentional orienting and disengagement: the effects of anodal tDCS over right posterior parietal cortex (PPC) and frontal eye field (FEF)

10.1101/2021.01.25.428095 ◽

2021 ◽

Author(s):

Lorenzo Diana ◽

Patrick Pilastro ◽

Edoardo N. Aiello ◽

Aleksandra K. Eberhard-Moscicka ◽

René M. Müri ◽

...

Keyword(s):

Parietal Cortex ◽

Posterior Parietal Cortex ◽

Right Hemisphere ◽

Reaction Times ◽

Gap Effect ◽

Frontal Eye Field ◽

Attentional Orienting ◽

Eye Field ◽

Posterior Parietal ◽

The Right

ABSTRACTIn the present work, we applied anodal transcranial direct current stimulation (tDCS) over the posterior parietal cortex (PPC) and frontal eye field (FEF) of the right hemisphere in healthy subjects to modulate attentional orienting and disengagement in a gap-overlap task. Both stimulations led to bilateral improvements in saccadic reaction times (SRTs), with larger effects for gap trials. However, analyses showed that the gap effect was not affected by tDCS. Importantly, we observed significant effects of baseline performance that may mediate side- and task-specific effects of brain stimulation.

Download Full-text

Lesions to right posterior parietal cortex impair visual depth perception from disparity but not motion cues

Philosophical Transactions of the Royal Society B Biological Sciences ◽

10.1098/rstb.2015.0263 ◽

2016 ◽

Vol 371 (1697) ◽

pp. 20150263 ◽

Cited By ~ 4

Author(s):

Aidan P. Murphy ◽

David A. Leopold ◽

Glyn W. Humphreys ◽

Andrew E. Welchman

Keyword(s):

Parietal Cortex ◽

Depth Perception ◽

Posterior Parietal Cortex ◽

Right Hemisphere ◽

3D Structure ◽

Three Dimensional ◽

Stimulus Presentation ◽

Visual Depth ◽

Posterior Parietal ◽

The Right

The posterior parietal cortex (PPC) is understood to be active when observers perceive three-dimensional (3D) structure. However, it is not clear how central this activity is in the construction of 3D spatial representations. Here, we examine whether PPC is essential for two aspects of visual depth perception by testing patients with lesions affecting this region. First, we measured subjects' ability to discriminate depth structure in various 3D surfaces and objects using binocular disparity. Patients with lesions to right PPC ( N = 3) exhibited marked perceptual deficits on these tasks, whereas those with left hemisphere lesions ( N = 2) were able to reliably discriminate depth as accurately as control subjects. Second, we presented an ambiguous 3D stimulus defined by structure from motion to determine whether PPC lesions influence the rate of bistable perceptual alternations. Patients' percept durations for the 3D stimulus were generally within a normal range, although the two patients with bilateral PPC lesions showed the fastest perceptual alternation rates in our sample. Intermittent stimulus presentation reduced the reversal rate similarly across subjects. Together, the results suggest that PPC plays a causal role in both inferring and maintaining the perception of 3D structure with stereopsis supported primarily by the right hemisphere, but do not lend support to the view that PPC is a critical contributor to bistable perceptual alternations. This article is part of the themed issue ‘Vision in our three-dimensional world’.

Download Full-text

Enhancing spatial reasoning by anodal transcranial direct current stimulation over the right posterior parietal cortex

Experimental Brain Research ◽

10.1007/s00221-019-05699-5 ◽

2019 ◽

Vol 238 (1) ◽

pp. 181-192

Author(s):

Julia Wertheim ◽

Lorenza S. Colzato ◽

Michael A. Nitsche ◽

Marco Ragni

Keyword(s):

Parietal Cortex ◽

Direct Current ◽

Transcranial Direct Current Stimulation ◽

Posterior Parietal Cortex ◽

Spatial Reasoning ◽

Direct Current Stimulation ◽

Posterior Parietal ◽

The Right

Download Full-text

Opposite biases in salience-based selection for the left and right posterior parietal cortex

Nature Neuroscience ◽

10.1038/nn1709 ◽

2006 ◽

Vol 9 (6) ◽

pp. 740-742 ◽

Cited By ~ 113

Author(s):

Carmel Mevorach ◽

Glyn W Humphreys ◽

Lilach Shalev

Keyword(s):

Parietal Cortex ◽

Posterior Parietal Cortex ◽

Posterior Parietal ◽

Left And Right ◽

Selection For

Download Full-text

Attentional bias to threat and gray mater volume morphology in high anxious individuals

10.1101/2020.10.20.346981 ◽

2020 ◽

Author(s):

Joshua M. Carlson ◽

Lin Fang

Keyword(s):

Attentional Bias ◽

Parietal Cortex ◽

Gray Matter ◽

Posterior Parietal Cortex ◽

Gray Matter Volume ◽

Anterior Cingulate ◽

Brain Morphology ◽

Matter Volume ◽

Posterior Parietal ◽

The Right

AbstractIn a sample of highly anxious individuals, the relationship between gray matter volume brain morphology and attentional bias to threat was assessed. Participants performed a dot-probe task of attentional bias to threat and gray matter volume was acquired from whole brain structural T1-weighted MRI scans. The results replicate previous findings in unselected samples that elevated attentional bias to threat is linked to greater gray matter volume in the anterior cingulate cortex, middle frontal gyrus, and striatum. In addition, we provide novel evidence that elevated attentional bias to threat is associated with greater gray matter volume in the right posterior parietal cortex, cerebellum, and other distributed regions. Lastly, exploratory analyses provide initial evidence that distinct sub-regions of the right posterior parietal cortex may contribute to attentional bias in a sex-specific manner. Our results illuminate how differences in gray matter volume morphology relate to attentional bias to threat in anxious individuals. This knowledge could inform neurocognitive models of anxiety-related attentional bias to threat and targets of neuroplasticity in anxiety interventions such as attention bias modification.

Download Full-text

Paired-Pulse Parietal-Motor Stimulation Differentially Modulates Corticospinal Excitability across Hemispheres When Combined with Prism Adaptation

Neural Plasticity ◽

10.1155/2016/5716179 ◽

2016 ◽

Vol 2016 ◽

pp. 1-9 ◽

Cited By ~ 8

Author(s):

Selene Schintu ◽

Elisa Martín-Arévalo ◽

Michael Vesia ◽

Yves Rossetti ◽

Romeo Salemme ◽

...

Keyword(s):

Left Hemisphere ◽

Posterior Parietal Cortex ◽

Right Hemisphere ◽

Motor Evoked Potentials ◽

Repetitive Transcranial Magnetic Stimulation ◽

Prism Adaptation ◽

Healthy Individuals ◽

Paired Pulse ◽

Posterior Parietal ◽

The Right

Rightward prism adaptation ameliorates neglect symptoms while leftward prism adaptation (LPA) induces neglect-like biases in healthy individuals. Similarly, inhibitory repetitive transcranial magnetic stimulation (rTMS) on the right posterior parietal cortex (PPC) induces neglect-like behavior, whereas on the left PPC it ameliorates neglect symptoms and normalizes hyperexcitability of left hemisphere parietal-motor (PPC-M1) connectivity. Based on this analogy we hypothesized that LPA increases PPC-M1 excitability in the left hemisphere and decreases it in the right one. In an attempt to shed some light on the mechanisms underlying LPA’s effects on cognition, we investigated this hypothesis in healthy individuals measuring PPC-M1 excitability with dual-site paired-pulse TMS (ppTMS). We found a left hemisphere increase and a right hemisphere decrease in the amplitude of motor evoked potentials elicited by paired as well as single pulses on M1. While this could indicate that LPA biases interhemispheric connectivity, it contradicts previous evidence that M1-only MEPs are unchanged after LPA. A control experiment showed that input-output curves were not affected by LPAper se. We conclude that LPA combined with ppTMS on PPC-M1 differentially alters the excitability of the left and right M1.

Download Full-text

Anodal High-definition Transcranial Direct Current Stimulation over the Posterior Parietal Cortex Modulates Approximate Mental Arithmetic

Journal of Cognitive Neuroscience ◽

10.1162/jocn_a_01514 ◽

2020 ◽

Vol 32 (5) ◽

pp. 862-876

Author(s):

Matthias Hartmann ◽

Sarah Singer ◽

Branislav Savic ◽

René M. Müri ◽

Fred W. Mast

Keyword(s):

Parietal Cortex ◽

Direct Current ◽

Transcranial Direct Current Stimulation ◽

Posterior Parietal Cortex ◽

Mental Arithmetic ◽

Cognitive Capacity ◽

High Definition ◽

Direct Current Stimulation ◽

Posterior Parietal ◽

Left And Right

The representation and processing of numerosity is a crucial cognitive capacity. Converging evidence points to the posterior parietal cortex (PPC) as primary “number” region. However, the exact role of the left and right PPC for different types of numerical and arithmetic tasks remains controversial. In this study, we used high-definition transcranial direct current stimulation (HD-tDCS) to further investigate the causal involvement of the PPC during approximative, nonsymbolic mental arithmetic. Eighteen healthy participants received three sessions of anodal HD-tDCS at 1-week intervals in counterbalanced order: left PPC, right PPC, and sham stimulation. Results showed an improved performance during online parietal HD-tDCS (vs. sham) for subtraction problems. Specifically, the general tendency to underestimate the results of subtraction problems (i.e., the “operational momentum effect”) was reduced during online parietal HD-tDCS. There was no difference between left and right stimulation. This study thus provides new evidence for a causal involvement of the left and right PPC for approximate nonsymbolic arithmetic and advances the promising use of noninvasive brain stimulation in increasing cognitive functions.

Download Full-text