Activity In Intraparietal Sulcus Research Articles

Distinct Neural Plasticity Enhancing Visual Perception.

The developed human brain shows remarkable plasticity following perceptual learning, resulting in improved visual sensitivity. However, such improvements commonly require extensive stimuli exposure. Here we show that efficiently enhancing visual perception with minimal stimuli exposure recruits distinct neural mechanisms relative to standard repetition-based learning. Participants (n = 20, 12 women, 8 men) encoded a visual discrimination task, followed by brief memory reactivations of only five trials each performed on separate days, demonstrating improvements comparable with standard repetition-based learning (n = 20, 12 women, 8 men). Reactivation-induced learning engaged increased bilateral intraparietal sulcus (IPS) activity relative to repetition-based learning. Complementary evidence for differential learning processes was further provided by temporal-parietal resting functional connectivity changes, which correlated with behavioral improvements. The results suggest that efficiently enhancing visual perception with minimal stimuli exposure recruits distinct neural processes, engaging higher-order control and attentional resources while leading to similar perceptual gains. These unique brain mechanisms underlying improved perceptual learning efficiency may have important implications for daily life and in clinical conditions requiring relearning following brain damage.

Stunting in infancy is associated with atypical activation of working memory and attention networks

Stunting is associated with poor long-term cognitive, academic and economic outcomes, yet the mechanisms through which stunting impacts cognition in early development remain unknown. In a first-ever neuroimaging study conducted on infants from rural India, we demonstrate that stunting impacts a critical, early-developing cognitive system—visual working memory. Stunted infants showed poor visual working memory performance and were easily distractible. Poor performance was associated with reduced engagement of the left anterior intraparietal sulcus, a region involved in visual working memory maintenance and greater suppression in the right temporoparietal junction, a region involved in attentional shifting. When assessed one year later, stunted infants had lower problem-solving scores, while infants of normal height with greater left anterior intraparietal sulcus activation showed higher problem-solving scores. Finally, short-for-age infants with poor physical growth indices but good visual working memory performance showed more positive outcomes suggesting that intervention efforts should focus on improving working memory and reducing distractibility in infancy.

P708. Temporal Discounting Rates Associated With Default Mode Network and Lateral Intraparietal Sulcus Activity in Patients At-Risk for Suicide Attempt

Temporal discounting is a neuroeconomics technique that can be used as a proxy measurement of impulsivity in clinical populations; however, little is known about the relationships between temporal discounting, suicide risk, and magnetoencephalography (MEG) oscillatory power.

Modifications in fMRI Representation of Mental Rotation Following a 6 Week Graded Motor Imagery Training in Chronic CRPS Patients

Complex regional pain syndrome (CRPS) is a neuropathic pain condition that is difficult to treat. For behavioral interventions, graded motor imagery (GMI) showed relevant effects, but underlying neural substrates in patient groups have not been investigated yet. A previous study investigating differences in the representation of a left/right hand judgment task demonstrated less recruitment of subcortical structures, such as the putamen, in CRPS patients than in healthy controls. In healthy volunteers, the putamen activity increased after a hand judgment task training. In order to test for longitudinal effects of GMI training, we investigated 20 CRPS patients in a wait-list crossover design with 3 evaluation time points. Patients underwent a 6 week GMI treatment and a 6 week waiting period in a randomized group assignment and treatment groups were evaluated by a blinded rater. When compared to healthy matched controls at baseline, CRPS patients showed less functional activation in areas processing visual input, left sensorimotor cortex, and right putamen. Only GMI treatment, but not the waiting period showed an effect on movement pain and hand judgment task performance. Regression analyses revealed positive associations of movement pain with left anterior insula activation at baseline. Right intraparietal sulcus activation change during GMI was associated with a gain in performance of the hand judgment task. The design used here is reliable for investigating the functional representation of the hand judgment task in an intervention study. PerspectiveTwenty chronic CRPS patients underwent a 6 week GMI intervention in a randomized wait-list crossover design. functional MRI was tested pre and post for the hand lateralization task which improved over GMI but not over WAITING. Performance gain was positively related to right parietal functional MRI activation.

Time ambiguity during intertemporal decision-making is aversive, impacting choice and neural value coding

We are often presented with choices that differ in their more immediate versus future consequences. Interestingly, in everyday-life, ambiguity about the exact timing of such consequences frequently occurs, yet it remains unknown whether and how time-ambiguity influences decisions and their underlying neural correlates. We developed a novel intertemporal fMRI choice task in which participants make choices between sooner-smaller (SS) versus later-larger (LL) monetary rewards with systematically varying levels of time-ambiguity. Across trials, delay information of the SS, the LL, or both rewards was either exact (e.g., in 5 weeks), of low ambiguity (4 week range: e.g., in 3–7 weeks), or of high ambiguity (8 week range: e.g., in 1–9 weeks). Choice behavior showed that the majority of participants preferred options with exact delays over those with ambiguous delays, indicating time-ambiguity aversion. Consistent with these results, the ventromedial prefrontal cortex showed decreased activation during ambiguous versus exact trials. In contrast, intraparietal sulcus activation increased during ambiguous versus exact trials. Furthermore, exploratory analyses suggest that more time-ambiguity averse participants show more insula and dorsolateral prefrontal cortex activation during subjective value (SV)-coding of ambiguous versus exact trials. Lastly, the best-fitting computational choice models indicate that ambiguity impacts the SV of options via time perception or via an additive ambiguity-related penalty term. Together, these results provide the first behavioral and neural signatures of time-ambiguity, pointing towards a unique profile that is distinct from impatience. Since time-ambiguity is ubiquitous in real-life, it likely contributes to shortsighted decisions above and beyond delay-discounting.

Fluency in symbolic arithmetic refines the approximate number system in parietal cortex.

The objective of this study was to investigate, using a brain measure of approximate number system (ANS) acuity, whether the precision of the ANS is crucial for the development of symbolic numerical abilities (i.e., scaffolding hypothesis) and/or whether the experience with symbolic number processing refines the ANS (i.e., refinement hypothesis). To this aim, 38 children solved a dot comparison task inside the scanner when they were approximately 10-years old (Time 1) and once again approximately 2 years later (Time 2). To study the scaffolding hypothesis, a regression analysis was carried out by entering ANS acuity at T1 as the predictor and symbolic math performance at T2 as the dependent measure. Symbolic math performance, visuospatial WM and full IQ (all at T1) were entered as covariates of no interest. In order to study the refinement hypothesis, the regression analysis included symbolic math performance at T1 as the predictor and ANS acuity at T2 as the dependent measure, while ANS acuity, visuospatial WM and full IQ (all at T1) were entered as covariates of no interest. Our results supported the refinement hypothesis, by finding that the higher the initial level of symbolic math performance, the greater the intraparietal sulcus activation was at T2 (i.e., more precise representation of quantity). To the best of our knowledge, our finding constitutes the first evidence showing that expertise in the manipulation of symbols, which is a cultural invention, has the power to refine the neural representation of quantity in the evolutionarily ancient, approximate system of quantity representation.

Parietal-Occipital Interactions Underlying Control- and Representation-Related Processes in Working Memory for Nonspatial Visual Features.

Although the manipulation of load is popular in visual working memory research, many studies confound general attentional demands with context binding by drawing memoranda from the same stimulus category. In this fMRI study of human observers (both sexes), we created high- versus low-binding conditions, while holding load constant, by comparing trials requiring memory for the direction of motion of one random dot kinematogram (RDK; 1M trials) versus for three RDKs (3M), or versus one RDK and two color patches (1M2C). Memory precision was highest for 1M trials and comparable for 3M and 1M2C trials. And although delay-period activity in occipital cortex did not differ between the three conditions, returning to baseline for all three, multivariate pattern analysis decoding of a remembered RDK from occipital cortex was also highest for 1M trials and comparable for 3M and 1M2C trials. Delay-period activity in intraparietal sulcus (IPS), although elevated for all three conditions, displayed more sensitivity to demands on context binding than to load per se. The 1M-to-3M increase in IPS signal predicted the 1M-to-3M declines in both behavioral and neural estimates of working memory precision. These effects strengthened along a caudal-to-rostral gradient, from IPS0 to IPS5. Context binding-independent load sensitivity was observed when analyses were lateralized and extended into PFC, with trend-level effects evident in left IPS and strong effects in left lateral PFC. These findings illustrate how visual working memory capacity limitations arise from multiple factors that each recruit dissociable brain systems.SIGNIFICANCE STATEMENT Visual working memory capacity predicts performance on a wide array of cognitive and real-world outcomes. At least two theoretically distinct factors are proposed to influence visual working memory capacity limitations: an amodal attentional resource that must be shared across remembered items; and the demands on context binding. We unconfounded these two factors by varying load with items drawn from the same stimulus category ("high demands on context binding") versus items drawn from different stimulus categories ("low demands on context binding"). The results provide evidence for the dissociability, and the neural bases, of these two theorized factors, and they specify that the functions of intraparietal sulcus may relate more strongly to the control of representations than to the general allocation of attention.

P 20 fMRI-associations with performance increase by mental imagery training of finger sequence

Objective Motor imagery (MI) is the mental simulation of action frequently used by professionals in different fields. The knowledge about changes in functional representation of motor patterns trained with mental imagery is sparse. In addition, we do not know how changes in functional representation during imagery training are associated with preciseness of imagined performance. We therefore intended to investigate changes in functional representation going along with performance changes (error, velocity) during a highly controlled (for intensity and temporal accuracy) mental imagery training (finger sequence performance) in 51 healthy young volunteers. Methods fMRI: mental imagery was measured with fMRI (3 Tesla, EPI with TR: 2 s) over 170 s pre and post training. Executed movements before and after training served for the assessment of training gain. Participants were instructed to move or to imagine moving the fingers of the right hand in a specific order in time with a 2 Hz blinking dot. Participants were given a key pad and were instructed to combine kinesthetic and visual imagery strategies. We tested the temporal congruence of the imagined finger sequence 10 times during training and rated imagery vividness on a 7-point Likert scale. Imaging analysis was performed using a full factorial design with SPM8 and a significance level of p . 05 , corrected for the whole brain volume (FWE). Linear regression (ROI-analysis for hippocampus, fusiform gyrus, BA 6, BA 44, parietal sulcus, cerebellar hemisphere; FWE; p . 05 ) was performed for performance changes over training (error, velocity) and scores during training for the changes for the MI-task over time. In addition, we tested whether training outcome (error, velocity) could be predicted by MI-pre-measurement. Results Performance increased for spatial accuracy (less errors; (t(47) = 1.99; p(one sided) = .026)) and velocity of finger movements (t(47) = 4.01; p = .001). For fMRI we found expected differences between the EX and MI task ( Fig. 1 , top left). Only the MI task showed fMRI-changes over time ( Fig. 1 , top right). fMRI-activation change in the fusiform gyrus went along with rated intensity of imagery during training ( Fig. 1 , bottom left). fMRI-activation intensity of left hippocampus during MIpre predicted spatial accuracy after training (error number low; Fig. 1 , bottom right). Conclusion Mental imagery minus execution of finger sequence showed increased intraparietal sulcus activation comparable to previous studies ( Boecker et al., 2002 ). Inferior left parietal activation during MI was increasing over training. The anterior hippocampus and the fusiform gyrus have been identified as important for spatial imagery before ( Jahn et al., 2009 ). Here we showed that the right anterior hippocampus during pre-training MI is predictive for spatial accuracy after training - a finding also reported before ( Huijbers et al., 2011 ). Only fMRI was capable of predicting spatial preciseness outcome but not imagery scores (MIQ, vividness). However, MI vividness rated during training was associated with increase of fusiform gyrus activation over training indicating high visual imagery strategies ( Huijbers et al., 2011 ).

Specialization of the Right Intraparietal Sulcus for Processing Mathematics During Development.

Mathematical ability, especially perception of numbers and performance of arithmetics, is known to rely on the activation of intraparietal sulcus (IPS). However, reasoning ability and working memory, 2 highly associated abilities also activate partly overlapping regions. Most studies aimed at localizing mathematical function have used group averages, where individual variability is averaged out, thus confounding the anatomical specificity when localizing cognitive functions. Here, we analyze the functional anatomy of the intraparietal cortex by using individual analysis of subregions of IPS based on how they are structurally connected to frontal, parietal, and occipital cortex. Analysis of cortical thickness showed that the right anterior IPS, defined by its connections to the frontal lobe, was associated with both visuospatial working memory, and mathematics in 6-year-old children. This region specialized during development to be specifically related to mathematics, but not visuospatial working memory in adolescents and adults. This could be an example of interactive specialization, where interacting with the environment in combination with interactions between cortical regions leads from a more general role of right anterior IPS in spatial processing, to a specialization of this region for mathematics.

What do we know about eye movements in Alzheimer's disease? The past 37 years and future directions.

What do we know about eye movements in Alzheimer's disease? The past 37 years and future directions.

Generalization in category learning: the roles of representational and decisional uncertainty.

Effective generalization in a multiple-category situation involves both assessing potential membership in individual categories and resolving conflict between categories while implementing a decision bound. We separated generalization from decision bound implementation using an information integration task in which category exemplars varied over two incommensurable feature dimensions. Human subjects first learned to categorize stimuli within limited training regions, and then, during fMRI scanning, they also categorized transfer stimuli from new regions of perceptual space. Transfer stimuli differed both in distance from the training region prototype and distance from the decision bound, allowing us to independently assess neural systems sensitive to each. Across all stimulus regions, categorization was associated with activity in the extrastriate visual cortex, basal ganglia, and the bilateral intraparietal sulcus. Categorizing stimuli near the decision bound was associated with recruitment of the frontoinsular cortex and medial frontal cortex, regions often associated with conflict and which commonly coactivate within the salience network. Generalization was measured in terms of greater distance from the decision bound and greater distance from the category prototype (average training region stimulus). Distance from the decision bound was associated with activity in the superior parietal lobe, lingual gyri, and anterior hippocampus, whereas distance from the prototype was associated with left intraparietal sulcus activity. The results are interpreted as supporting the existence of different uncertainty resolution mechanisms for uncertainty about category membership (representational uncertainty) and uncertainty about decision bound (decisional uncertainty).

Cortical activity modulation by botulinum toxin type A in patients with post-stroke arm spasticity: Real and imagined hand movement

BackgroundOur aim was to use functional magnetic resonance imaging (fMRI) to compare brain activation changes due to botulinum toxin A (BoNT) application between two chronic stroke patient groups with different degree of weakness treated for upper limb spasticity. MethodsFourteen ischemic stroke patients with hand weakness and spasticity were studied. Spasticity was scored by modified Ashworth scale (MAS). FMRI was performed 3 times: before (W0) and 4 (W4) and 11weeks (W11) after BoNT application. Group A: 7 patients (2 males, 5 females; mean age 59.14years) with hand plegia, who imagined moving fingers. Group B: 7 age-matched patients (6 males, 1 female; mean age 59.57years) able to perform sequential finger movement. ResultsBoNT transiently lowered MAS in W4 in both groups. In group A, activation of the frontal premotor cortex dominated and persisted for all three fMRI sessions whereas the ipsilesional cerebellum and cortex bordering bilateral intraparietal sulcus activation changed over time. Between-session contrasts showed treatment-related activation decreases in the mesial occipitoparietal and lateral occipital cortex. In group B, brain activation was markedly reduced after BoNT (W4). Whereas some of these areas manifested only transient reduction and expanded again at W11, in others the reduction persisted. ConclusionStudy of two age-matched groups with mild and severe weakness demonstrated different effects of BoNT-lowered spasticity on sensorimotor networks. Group A performing movement imagery manifested BoNT-induced reduction of activation in structures associated with visual imagery. Group B performing movement manifested reduced activation extent and reduced activation of structures outside classical motor system, suggestive of motor network normalization.

The Value of Numbers in Economic Rewards

Previous work has identified a distributed network of neural systems involved in appraising the value of rewards, such as when winning $100 versus $1. These studies, however, confounded monetary value and the number used to represent it, which leads to the possibility that some elements in the network may be specialized for processing numeric rather than monetary value. To test this hypothesis, we manipulated numeric magnitude and units to construct a range of economic rewards for simple decisions (e.g., 1¢, $1, 100¢, $100). Consistent with previous research in numerical cognition, results showed that blood-oxygen-level-dependent (BOLD) activity in intraparietal sulcus was correlated with changes in numeric magnitude, independent of monetary value, whereas activity in orbitofrontal cortex was correlated with monetary value, independent of numeric magnitude. Finally, region-of-interest analyses revealed that the BOLD response to numeric magnitude, but not monetary value, described a compressive function. Together, these findings highlight the importance of numerical cognition for understanding how the brain processes monetary rewards.

Intraparietal sulcus activity during explicit self-referential social status judgments about others

Previous research has suggested that the intraparietal sulcus (IPS) supports judgments of social distance, with greater activity observed in response to targets judged to be closer to each other (Yamakawa, Kanai, Matsumura, & Naito, 2009). Amongst other stimuli, activity in the IPS appears to be responsive to targets varying in social status (Chiao et al., 2009; Cloutier, Ambady, Meagher, & Gabrieli, 2012). The current project examined brain responses during explicit self-referential social status judgments of targets varying in either financial or moral status. Using an event-related fMRI design, participants viewed photographs of male faces paired with distinct levels of financial or moral status. During the task, participants were asked to explicitly identify each target’s status in relation to their own. Focusing on IPS activity, results from whole-brain and region of interest analyses revealed an interaction between social status types and levels. The implications of these results are discussed with respect to our current understanding of the impact of social status on the neural substrates of person perception.

Different Levels of Activity in the Left Intraparietal Sulcus Triggered by Lasting and Unlasting Cues in the Posner Task

In experimental paradigms, voluntary orienting of visual-spatial attention is conventionally achieved through the Posner task in which predictive central cues remain present until target offset (lasting cue) or disappear prior to target onset (unlasting cue). Previous studies have implied that lasting and unlasting cues elicit different levels of activity in the intraparietal sulcus (IPS). However, no study to date has directly compared the neural correlates of visual-spatial attention under unlasting versus lasting cue conditions. We investigated the neural mechanisms involved in the processing of both types of cues using functional magnetic resonance imaging (fMRI). Behaviorally, subjects exhibited no difference in the two cue type conditions. However, neuroimaging data revealed increased activation of the left IPS in the unlasting cue condition. We propose that in the unlasting cue condition, the time interval between the onsets of cue and target requires subjects to maintain a location in spatial working memory. This hypothesis suggests that the difference in activity in the left IPS between lasing and unlasting cue conditions is the neural correlate of spatial working memory. Keywords: Functional magnetic resonance imaging (fMRI), intraparietal sulcus (IPS), posner task, spatial working memory, visual-spatial attention.

Number–Space Interactions in the Human Parietal Cortex: Enlightening the SNARC Effect with Functional Near-Infrared Spectroscopy

Interactions between numbers and space have become a major issue in cognitive neuroscience, because they suggest that numerical representations might be deeply rooted in cortical networks that also subserve spatial cognition. The spatial-numerical association of response codes (SNARC) is the most robust and widely replicated demonstration of the link between numbers and space: in magnitude comparison or parity judgments, participants' reaction times to small numbers are faster with left than right effectors, whereas the converse is found for large numbers. However, despite the massive body of research on number-space interactions, the nature of the SNARC effect remains controversial and no study to date has identified its hemodynamic correlates. Using functional near-infrared spectroscopy, we found a hemodynamic signature of the SNARC effect in the bilateral intraparietal sulcus, a core region for numerical magnitude representation, and left angular gyrus (ANG), a region implicated in verbal number processing. Activation of intraparietal sulcus was also modulated by numerical distance. Our findings point to number semantics as cognitive locus of number-space interactions, thereby revealing the intrinsic spatial nature of numerical magnitude representation. Moreover, the involvement of left ANG is consistent with the mediating role of verbal/cultural factors in shaping interactions between numbers and space.

Understanding less than nothing: Neural distance effects for negative numbers

Little work has examined how the mental number system accommodates counterintuitive quantities such as negative numbers, which seem to extend the left end of the mental number line and reverse the established relationship between digit magnitude and value; even less research has been conducted on the neural systems supporting negative number understanding. This study aimed to determine whether adult behavioral and neural responses to negative number paired comparisons were similar to those expected for positive numbers. Mixed pairs (with one positive and one negative number) were also included. Negative number responses demonstrated an increased typical distance effect relative to that for positives, with decreasing response times and intraparietal sulcus activity for comparisons farther apart than those closer together. Negative pairs also showed more activity than positive comparisons across distances in the occipital lobe, inferior and superior parietal lobule, and bilateral caudate and putamen. Mixed pair effect direction varied based on polarity sensitivity, or whether attention to the negative sign was needed for accurate responses, indicating differences in processing strategy. Adults thus draw on brain areas important in numeric processing when dealing with negatives, but also recruit further areas and strategies to support the unique features of negative numbers. The increased distance effect seen may reflect a less mature understanding of negatives. This work expands our knowledge of the flexibility of the mental number system and its ability to represent difficult quantities.

Differential roles of inferior frontal and inferior parietal cortex in task switching: Evidence from stimulus‐categorization switching and response‐modality switching

We used fMRI to investigate both common and differential neural mechanisms underlying two distinct types of switching requirements, namely switching between stimulus categorizations (color vs. form) and switching between response modalities (hand vs. foot responses). Both types of switching induced similar behavioral shift costs. However, at the neural level, switching between stimulus categorizations led to left-hemispheric activations including the inferior frontal gyrus as well as the intraparietal sulcus extending to the superior parietal gyrus and the supramarginal gyrus. In contrast, switching between response modalities was associated mainly with left-hemispheric activation of the intraparietal sulcus and the supramarginal gyrus. A conjunction analysis indicated common activation of the left intraparietal sulcus and the supramarginal gyrus for both types of switching. Together, these results qualify previous claims about a general role of the left prefrontal cortex in task control by suggesting that the left inferior frontal gyrus is specifically involved in switching between stimulus categorizations, whereas parietal cortex is more generally implicated in the selection of action rules.

Numeric aspects in pitch identification: an fMRI study

BackgroundPitch identification had yielded unique response patterns compared to other auditory skills. Selecting one out of numerous pitches distinguished this task from detecting a pitch ascent. Encoding of numerous stimuli had activated the intraparietal sulcus in the visual domain. Therefore, we hypothesized that numerosity encoding during pitch identification activates the intraparietal sulcus as well.MethodsTo assess pitch identification, the participants had to recognize a single pitch from a set of four possible pitches in each trial. Functional magnetic resonance imaging (fMRI) disentangled neural activation during this four-pitch-choice task from activation during pitch contour perception, tone localization, and pitch discrimination.ResultsPitch identification induced bilateral activation in the intraparietal sulcus compared to pitch discrimination. Correct responses in pitch identification correlated with activation in the left intraparietal sulcus. Pitch contour perception activated the superior temporal gyrus conceivably due to the larger range of presented tones. The differentiation between pitch identification and tone localization failed. Activation in an ACC-hippocampus network distinguished pitch discrimination from pitch identification.ConclusionPitch identification is distinguishable from pitch discrimination on the base of activation in the IPS. IPS activity during pitch identification may be the auditory counterpart of numerosity encoding in the visual domain.

Neural Basis of Visual Distraction

The ability to maintain focus and avoid distraction by goal-irrelevant stimuli is critical for performing many tasks and may be a key deficit in attention-related problems. Recent studies have demonstrated that irrelevant stimuli that are consciously perceived may be filtered out on a neural level and not cause the distraction triggered by subliminal stimuli. However, in everyday situations, suprathreshold stimuli often do capture attention, but the neural mechanisms by which some stimuli rapidly and automatically trigger distraction remain unknown. Here, we investigated the neural basis of distraction by utilizing a particularly strong form of distractor: the abrupt appearance of a new object. Our results revealed a competitive relation between brain regions coding the locations of the target and the distractor, with distractor processing increasing and target processing decreasing, but only when the distractor was a new object; an equivalent luminance change to an existing object neither generated distraction nor affected target processing. Results also revealed changes in neural activity in intraparietal sulcus (IPS) and temporo-parietal junction (TPJ) that were unique to the new object distractor condition. The strongest relations between behavioral distraction and neural activity were observed in these parietal regions. Furthermore, participants who were less susceptible to distraction showed a more consistent, albeit more moderate, level of activity in IPS and TPJ. The present results thus provide new evidence regarding the neural mechanisms underlying distraction and resistance to it.