The neural basis of hand choice: An fMRI investigation of the Posterior Parietal Interhemispheric Competition model

AbstractThe current study investigates a new neurobiological model of human hand choice: The Posterior Parietal Interhemispheric Competition (PPIC) model. The model specifies that neural populations in bilateral posterior intraparietal and superior parietal cortex (pIP-SPC) encode actions in hand-specific terms, and compete for selection across and within hemispheres. Actions with both hands are encoded bilaterally, but the contralateral hand is overrepresented. We use a novel fMRI paradigm to test the PPIC model. Participants reach to visible targets while in the scanner, and conditions involving free choice of which hand to use (Choice) are compared with when hand-use is instructed. Consistent with the PPIC model, bilateral pIP-SPC is preferentially responsive for the Choice condition, and for actions made with the contralateral hand. In the right pIP-SPC, these effects include anterior intraparietal and superior parieto-occipital cortex. Left dorsal premotor cortex, and an area in the right lateral occipitotemporal cortex show the same response pattern, while the left inferior parietal lobule is preferentially responsive for the Choice condition and when using the ipsilateral hand. Behaviourally, hand choice is biased by target location – for targets near the left/right edges of the display, the hand in ipsilateral hemispace is favoured. Moreover, consistent with a competitive process, response times are prolonged for choices to more ambiguous targets, where hand choice is relatively unbiased, and fMRI responses in bilateral pIP-SPC parallel this pattern. Our data provide support for the PPIC model, and reveal a selective network of brain areas involved in free hand choice, including bilateral posterior parietal cortex, left-lateralized inferior parietal and dorsal premotor cortices, and the right lateral occipitotemporal cortex.

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The Role of the Right Posterior Parietal Cortex in Letter Migration between Words

Journal of Cognitive Neuroscience ◽

10.1162/jocn_a_00713 ◽

2015 ◽

Vol 27 (2) ◽

pp. 377-386 ◽

Cited By ~ 2

Author(s):

Dario Cazzoli ◽

René M. Müri ◽

Christopher Kennard ◽

Clive R. Rosenthal

Keyword(s):

Parietal Cortex ◽

Posterior Parietal Cortex ◽

Word Reading ◽

Letter Position ◽

Control Group ◽

Neural Basis ◽

Specific Effects ◽

Letter Position Coding ◽

Posterior Parietal ◽

The Right

When briefly presented with pairs of words, skilled readers can sometimes report words with migrated letters (e.g., they report hunt when presented with the words hint and hurt). This and other letter migration phenomena have been often used to investigate factors that influence reading such as letter position coding. However, the neural basis of letter migration is poorly understood. Previous evidence has implicated the right posterior parietal cortex (PPC) in processing visuospatial attributes and lexical properties during word reading. The aim of this study was to assess this putative role by combining an inhibitory TMS protocol with a letter migration paradigm, which was designed to examine the contributions of visuospatial attributes and lexical factors. Temporary interference with the right PPC led to three specific effects on letter migration. First, the number of letter migrations was significantly increased only in the group with active stimulation (vs. a sham stimulation group or a control group without stimulation), and there was no significant effect on other error types. Second, this effect occurred only when letter migration could result in a meaningful word (migration vs. control context). Third, the effect of active stimulation on the number of letter migrations was lateralized to target words presented on the left. Our study thus demonstrates that the right PPC plays a specific and causal role in the phenomenon of letter migration. The nature of this role cannot be explained solely in terms of visuospatial attention, rather it involves an interplay between visuospatial attentional and word reading-specific factors.

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Transcranial direct current stimulation of the posterior parietal cortex biases human hand choice

Scientific Reports ◽

10.1038/s41598-020-80611-8 ◽

2021 ◽

Vol 11 (1) ◽

Author(s):

Kento Hirayama ◽

Takayuki Koga ◽

Toru Takahashi ◽

Rieko Osu

Keyword(s):

Reaction Time ◽

Parietal Cortex ◽

Direct Current ◽

Transcranial Direct Current Stimulation ◽

Posterior Parietal Cortex ◽

Human Hand ◽

Direct Current Stimulation ◽

Posterior Parietal ◽

The Right ◽

Stimulation Of

AbstractHand choices—deciding which hand to use to reach for targets—represent continuous, daily, unconscious decisions. The posterior parietal cortex (PPC) contralateral to the selected hand is activated during a hand-choice task, and disruption of left PPC activity with a single-pulse transcranial magnetic stimulation prior to the execution of the motion suppresses the choice to use the right hand but not vice versa. These findings imply the involvement of either bilateral or left PPC in hand choice. To determine whether the effects of PPC’s activity are essential and/or symmetrical in hand choice, we increased or decreased PPC excitability in 16 healthy participants using transcranial direct current stimulation (tDCS; 10 min, 2 mA, 5 × 7 cm) and examined its online and residual effects on hand-choice probability and reaction time. After the right PPC was stimulated with an anode and the left PPC with a cathode, the probability of left-hand choice significantly increased and reaction time significantly decreased. However, no significant changes were observed with the stimulation of the right PPC with a cathode and the left PPC with an anode. These findings, thus, reveal the asymmetry of PPC-mediated regulation in hand choice.

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Integration of Target and Effector Information in the Human Brain During Reach Planning

Journal of Neurophysiology ◽

10.1152/jn.00456.2006 ◽

2007 ◽

Vol 97 (1) ◽

pp. 188-199 ◽

Cited By ~ 132

Author(s):

S. M. Beurze ◽

F. P. de Lange ◽

I. Toni ◽

W. P. Medendorp

Keyword(s):

Parietal Cortex ◽

Posterior Parietal Cortex ◽

Human Subjects ◽

Premotor Cortex ◽

Insular Cortex ◽

Spatial Location ◽

Posterior Parietal ◽

The Right ◽

Integrative Processing ◽

Reach Planning

To plan a reaching movement, the brain must integrate information about the location of the target with information about the limb selected for the reach. Here, we applied rapid event-related 3-T fMRI to investigate this process in human subjects ( n = 16) preparing a reach following two successive visual instruction cues. One cue instructed which arm to use; the other cue instructed the location of the reach target. We hypothesized that regions involved in the integration of target and effector information should not only respond to each of the two instruction cues, but should respond more strongly to the second cue due to the added integrative processing to establish the reach plan. We found bilateral regions in the posterior parietal cortex, the premotor cortex, the medial frontal cortex, and the insular cortex to be involved in target–arm integration, as well as the left dorsolateral prefrontal cortex and an area in the right lateral occipital sulcus to respond in this manner. We further determined the functional properties of these regions in terms of spatial and effector specificity. This showed that the posterior parietal cortex and the dorsal premotor cortex specify both the spatial location of a target and the effector selected for the response. We therefore conclude that these regions are selectively engaged in the neural computations for reach planning, consistent with the results from physiological studies in nonhuman primates.

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Integration of Target and Effector Information in Human Posterior Parietal Cortex for the Planning of Action

Journal of Neurophysiology ◽

10.1152/jn.00725.2004 ◽

2005 ◽

Vol 93 (2) ◽

pp. 954-962 ◽

Cited By ~ 120

Author(s):

W. Pieter Medendorp ◽

Herbert C. Goltz ◽

J. Douglas Crawford ◽

Tutis Vilis

Keyword(s):

Parietal Cortex ◽

Posterior Parietal Cortex ◽

Spatial Information ◽

Target Location ◽

Premotor Cortex ◽

Target Selection ◽

Right Hand ◽

Pointing Movements ◽

Posterior Parietal ◽

The Right

Recently, using event-related functional MRI (fMRI), we located a bilateral region in the human posterior parietal cortex (retIPS) that topographically represents and updates targets for saccades and pointing movements in eye-centered coordinates. To generate movements, this spatial information must be integrated with the selected effector. We now tested whether the activation in retIPS is dependent on the hand selected. Using 4-T fMRI, we compared the activation produced by movements, using either eyes or the left or right hand, to targets presented either leftward or rightward of central fixation. The majority of the regions activated during saccades were also activated during pointing movements, including occipital, posterior parietal, and premotor cortex. The topographic retIPS region was activated more strongly for saccades than for pointing. The activation associated with pointing was significantly greater when pointing with the unseen hand to targets ipsilateral to the hand. For example, although there was activation in the left retIPS when pointing to targets on the right with the left hand, the activation was significantly greater when using the right hand. The mirror symmetric effect was observed in the right retIPS. Similar hand preferences were observed in a nearby anterior occipital region. This effector specificity is consistent with previous clinical and behavioral studies showing that each hand is more effective in directing movements to targets in ipsilateral visual space. We conclude that not only do these regions code target location, but they also appear to integrate target selection with effector selection.

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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

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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.

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