Spatial Task Performance Research Articles

Two intrinsic coupling types for resting-state integration in the human brain.

Recent findings indicate that synchronous neural activity at rest influences human performance in subsequent tasks. Synchronization can occur in form of phase coupling or amplitude correlation. It is unknown whether these coupling types have differing behavioral significance at rest. To address this, we performed resting-state electroencephalography (EEG) and source connectivity analysis in several populations of healthy subjects and patients with brain lesions. We systematically compared different types and frequencies of neural synchronization and investigated their association with behavioral performance in verbal and spatial attention tasks. Behavioral performance could be consistently predicted by two distinct resting-state coupling patterns: (1) amplitude envelope correlation of beta activity between homologous areas of both hemispheres, (2) lagged phase synchronization in EEG alpha activity between a brain area and the entire cortex. A disruption of these coupling patterns was also associated with neurological deficits in patients with stroke lesions. This suggests the existence of two distinct network systems responsible for resting-state integration. Lagged phase synchronization in the alpha band is associated with global interaction across networks while amplitude envelope correlation seems to be behaviorally relevant for interactions within networks and between hemispheres. These two coupling types may therefore provide complementary insights on brain physiology and pathology.

Visual Memory in Unilateral Spatial Neglect: Immediate Recall versus Delayed Recognition

Patients with unilateral spatial neglect (USN) often show impaired performance in spatial working memory tasks, apart from the difficulty retrieving "left-sided" spatial data from long-term memory, shown in the "piazza effect" by Bisiach and colleagues. This study's aim was to compare the effect of the spatial position of a visual object on immediate and delayed memory performance in USN patients. Specifically, immediate verbal recall performance, tested using a simultaneous presentation of four visual objects in four quadrants, was compared with memory in a later-provided recognition task, in which objects were individually shown at the screen center. Unlike healthy controls, USN patients showed a left-side disadvantage and a vertical bias in the immediate free recall task (69% vs. 42% recall for right- and left-sided objects, respectively). In the recognition task, the patients correctly recognized half of "old" items, and their correct rejection rate was 95.5%. Importantly, when the analysis focused on previously recalled items (in the immediate task), no statistically significant difference was found in the delayed recognition of objects according to their original quadrant of presentation. Furthermore, USN patients were able to recollect the correct original location of the recognized objects in 60% of the cases, well beyond chance level. This suggests that the memory trace formed in these cases was not only semantic but also contained a visuospatial tag. Finally, successful recognition of objects missed in recall trials points to formation of memory traces for neglected contralesional objects, which may become accessible to retrieval processes in explicit memory.

Otoconia-deficient mice show selective spatial deficits.

The vestibular system contributes to the performance of various spatial memory tasks, but few studies have attempted to disambiguate the roles of the semicircular canals and otolith organs in this performance. This study tested the otolithic contribution to spatial working and reference memory by evaluating the performance of otoconia-deficient tilted mice on a radial arm maze and a Barnes maze. One radial arm maze task provided both intramaze and extramaze cues, whereas the other task provided only extramaze cues. The Barnes maze task provided only extramaze cues. On the radial arm maze, tilted mice performed similar to control mice when intramaze cues were available, but committed more working and reference memory errors than control mice when only extramaze cues were available. On the Barnes maze task, control and tilted mice showed similar latency, distance, and errors during acquisition training. On the subsequent probe trial, both groups spent the greatest percentage of time in the goal quadrant, indicating they were able to use extramaze cues to guide their search. Overall, these results suggest signals originating in the otolith organs contribute to spatial memory, but are not necessary for all aspects of spatial performance.

Working Memory and Facial Expression Recognition in Patients with Parkinson’s Disease

Facial expression recognition impairment has been reported in Parkinson's disease. While some authors have referred to specific emotional disabilities, others view them as secondary to executive deficits frequently described in the disease, such as working memory. The present study aims to analyze the relationship between working memory and facial expression recognition abilities in Parkinson's disease. We observed 50 patients with Parkinson's disease and 49 healthy controls by means of an n-back procedure with four types of stimuli: emotional facial expressions, gender, spatial locations, and non-sense syllables. Other executive and visuospatial neuropsychological tests were also administered. Results showed that Parkinson's disease patients with high levels of disability performed worse than healthy individuals on the emotional facial expression and spatial location tasks. Moreover, spatial location task performance was correlated with executive neuropsychological scores, but emotional facial expression was not. Thus, working memory seems to be altered in Parkinson's disease, particularly in tasks that involve the appreciation of spatial relationships in stimuli. Additionally, non-executive, facial emotional recognition difficulty seems to be present and related to disease progression.

The relationship between mental rotations ability, eye movement patterns, and spatial task performance (535.7)

Mental rotations ability (MRA), a subset of spatial ability, is linked to success in anatomy and the STEMM disciplines. Like any ability, MRA differs in the general population. Some people can mentally rotate 2D and 3D objects with ease, while others have difficulty with these mental tasks. Previous research suggests that the cognitive processes underlying MRA are manifest in eye‐movements. However, research has focused primarily on describing how individuals of high and low‐MRA differ in eye‐movement patterns rather than demonstrating how knowledge of these differences can be used to improve observational approaches and learning. This study aims to determine whether the eye‐movement patterns (frequency of fixation, duration of fixation, salient features, and average visual scan path) of high‐MRA individuals can be used to improve spatial task performance for low‐MRA individuals. Undergraduate students at Western University will complete a standardized test of MRA (Shepard and Metzler Mental Rotations Test) while eye‐movement metrics are collected. The eye‐movement patterns of high‐MRA individuals will then be used to train low‐MRA individuals to improve performance on subsequent spatial tests. Results from these studies may be employed to guide the design and delivery of innovative eye‐movement based approaches to improve instruction in anatomy and other STEMM disciplines.

Aldehyde dehydrogenase 2 null mice as an oxidative stress‐based model of age‐related cognitive impairment with Alzheimer’s disease‐like pathologies (845.3)

Most current mouse models Alzheimer’s disease (AD) exhibit pathological changes dependent on overexpression of mutant human genes linked to familial AD, and animal models that mirror late‐onset/age‐related AD (95% of AD cases) are lacking. Oxidative stress is considered a causative factor in age‐related AD, and Aldehyde dehydrogenase 2 (ALDH2) is important for the detoxification of endogenous aldehydes, such as 4‐hydroxynonenal (HNE), a lipid peroxidation product formed during periods of oxidative stress that can form protein adducts, altering cell function. HNE adducts accumulate in the brains of AD patients and are associated with AD pathology. Given this linkage, manipulations that increase HNE levels might be expected to result in biochemical and cognitive changes that mirror those found in AD. Accordingly, we followed the age‐related changes of a number of relevant AD markers over a 12 month period in hippocampal homogenates from Aldh2 null mice. Marked increases in HNE adduct formation occurred as early as 3 months, and there were age‐related increases in monomeric amyloid β (Aβ), phospho tau protein, and activated caspases 3 and 6. Also observed were age‐related decreases in PSD95 and synaptophysin (indicating synaptic loss) and of total and phosphorylated cAMP‐response element binding protein (CREB). Aldh2 null mice exhibit a graded, age‐related decrease in performance in recognition and spatial memory tasks beginning at 3 months of age and maximal at 6 months. These mice also exhibit dystrophic neurites and loss of dendritic spines, defects in cholinergic agonist‐induced CREB phosphorylation, endothelial dysfunction, and monomeric and oligomeric Aβ deposition in cerebral microvessels. Aldh2 null mice exhibit a wide spectrum of AD‐like pathological changes that are rarely observed together in current AD animal models, and may prove useful for assessing the efficacy of therapeutic agents for improving memory and for slowing, preventing, or reversing disease progression.Grant Funding Source: Botterell Foundation

Effects of VR System Fidelity on Analyzing Isosurface Visualization of Volume Datasets

Volume visualization is an important technique for analyzing datasets from a variety of different scientific domains. Volume data analysis is inherently difficult because volumes are three-dimensional, dense, and unfamiliar, requiring scientists to precisely control the viewpoint and to make precise spatial judgments. Researchers have proposed that more immersive (higher fidelity) VR systems might improve task performance with volume datasets, and significant results tied to different components of display fidelity have been reported. However, more information is needed to generalize these results to different task types, domains, and rendering styles. We visualized isosurfaces extracted from synchrotron microscopic computed tomography (SR-μCT) scans of beetles, in a CAVE-like display. We ran a controlled experiment evaluating the effects of three components of system fidelity (field of regard, stereoscopy, and head tracking) on a variety of abstract task categories that are applicable to various scientific domains, and also compared our results with those from our prior experiment using 3D texture-based rendering. We report many significant findings. For example, for search and spatial judgment tasks with isosurface visualization, a stereoscopic display provides better performance, but for tasks with 3D texture-based rendering, displays with higher field of regard were more effective, independent of the levels of the other display components. We also found that systems with high field of regard and head tracking improve performance in spatial judgment tasks. Our results extend existing knowledge and produce new guidelines for designing VR systems to improve the effectiveness of volume data analysis.

High and low schizotypal female subjects do not differ in spatial memory abilities in a virtual reality task

Introduction. Schizotypy is a psychological construct related to schizophrenia. The exact relationship between both entities is not clear. In recent years, schizophrenia has been associated with hippocampal abnormalities and spatial memory problems. The aim of this study was to determine possible links between high schizotypy (HS) and low schizotypy (LS) and spatial abilities, using virtual reality tasks. We hypothesised that the HS group would exhibit a lower performance in spatial memory tasks than the LS group.Methods. Two groups of female students were formed according to their score on the ESQUIZO-Q-A questionnaire. HS and LS subjects were tested on two different tasks: the Boxes Room task, a spatial memory task sensitive to hippocampal alterations and a spatial recognition task.Results. Data showed that both groups mastered both tasks. Groups differed in personality features but not in spatial performance. These results provide valuable information about the schizotypy–schizophrenia connections.Conclusion. Schizotypal subjects are not impaired on spatial cognition and, accordingly, the schizotypy–schizophrenia relationship is not straightforward.

Presentation and production: The role of gesture in spatial communication

During social interaction, verbal language as well as nonverbal behavior is exchanged between speakers and listeners. One social task that often involves nonverbal behavior is the relaying of spatial direction information. The questions addressed in this study were whether presenting gesture during encoding (a) enhanced corresponding spatial task performance and (b) elicited gesture production at recall for adults and children. Children (3–4years) and adults were presented with verbal route directions through a small-scale spatial array and, depending on the assigned condition (i.e., no gestures, beat gestures, or representational gestures), the accompanying gestures. Children, but not adults, benefited from the presence of gesture during encoding of the spatial route direction task, as measured by recall at test. Results suggest that the presence of gesture during encoding plays an integral part of effectively communicating spatial route direction information, particularly for children.

Possible Mechanisms for the Effects of Orexin on Hippocampal Functioning and Spatial Learning (analytical review)

Orexin (hypocretin) is one of the key neuropeptidesresponsible for controlling the sleep-waking cycle [3, 64].This substance is required for transition to the state of wak-ing, while antagonists of orexin-sensitive receptors effec-tively prevent sleeplessness [64] and the death of orexin-releasing neurons leads to narcolepsy [8, 15]. Thisneuropeptide, released by a small group of neurons in thelateral and posterior hypothalamus, acts via type 1 G-pro-tein-coupled receptors (OX1) sensitive mainly to orexin A(hypocretin 1) and type 2 receptors (OX2) sensitive to bothorexin B (hypocretin 2) and orexin A [3]. Recent studieshave shown that orexin modulates the activity of neurons incircuits involved in reinforcement-mediated learning [22,64]. Thus, OX1 receptor antagonists have been found tocounter the reinforcing effects of narcotics and foodstuffs,while blockade of OX2 receptors decreases the reinforcingeffects of ethanol [51]. Orexin appears to be able to takepart in the processes forming various types of behavior, asneurons in the lateral hypothalamus releasing this neu-ropeptide innervate many CNS structures, including theforebrain, thalamus, hippocampus, septum, basal ganglia,dopaminergic nuclei, dorsal raphe nuclei, and the amyg-dala, i.e., structures involved in transmitting informationand regulating motor activity, spatial perception, and themechanisms of reinforcement [36, 39, 44, 46, 47]. Orexinhas been shown to influence the performance of spatialtasks requiring involvement of the hippocampus. Thus,administration of a selective OX1 receptor antagonist intofield CA1 led to impairment of the processes of consolida-tion and extraction of information from memory relating totraining in the Morris water maze [11]. Administration of anOX1 receptor antagonist into the dentate gyrus also degrad-ed memory for information associated with training in thewater maze [10]. It should be noted, however, that systemic

KIBRA (KIdney/BRAin protein) regulates learning and memory and stabilizes Protein kinase Mζ

The WWC1 gene has been genetically associated with human episodic memory performance, and its product KIdney/BRAin protein (KIBRA) has been shown to interact with the atypical protein kinase protein kinase M ζ (PKMζ). Although recently challenged, PKMζ remains a candidate postsynaptic regulator of memory maintenance. Here, we show that PKMζ is subject to rapid proteasomal degradation and that KIBRA is both necessary and sufficient to counteract this process, thus stabilizing the kinase and maintaining its function for a prolonged time. We define the binding sequence on KIBRA, a short amino acid motif near the C-terminus. Both hippocampal knock-down of KIBRA in rats and KIBRA knock-out in mice result in decreased learning and memory performance in spatial memory tasks supporting the notion that KIBRA is a player in episodic memory. Interestingly, decreased memory performance is accompanied by decreased PKMζ protein levels. We speculate that the stabilization of synaptic PKMζ protein levels by KIBRA may be one mechanism by which KIBRA acts in memory maintenance. KIBRA/WWC1 has been genetically associated with human episodic memory. KIBRA has been shown to be post-synaptically localized, but its function remained obscure. Here, we show that KIBRA shields PKMζ, a kinase previously linked to memory maintenance, from proteasomal degradation via direct interaction. KIBRA levels in the rodent hippocampus correlate closely both to spatial memory performance in rodents and to PKMζ levels. Our findings support a role for KIBRA in memory, and unveil a novel function for this protein.

Visuospatial anatomy comprehension: The role of spatial visualization ability and problem‐solving strategies

The present study explored the problem-solving strategies of high- and low-spatial visualization ability learners on a novel spatial anatomy task to determine whether differences in strategies contribute to differences in task performance. The results of this study provide further insights into the processing commonalities and differences among learners beyond the classification of spatial visualization ability alone, and help elucidate what, if anything, high- and low-spatial visualization ability learners do differently while solving spatial anatomy task problems. Forty-two students completed a standardized measure of spatial visualization ability, a novel spatial anatomy task, and a questionnaire involving personal self-analysis of the processes and strategies used while performing the spatial anatomy task. Strategy reports revealed that there were different ways students approached answering the spatial anatomy task problems. However, chi-square test analyses established that differences in problem-solving strategies did not contribute to differences in task performance. Therefore, underlying spatial visualization ability is the main source of variation in spatial anatomy task performance, irrespective of strategy. In addition to scoring higher and spending less time on the anatomy task, participants with high spatial visualization ability were also more accurate when solving the task problems.

Early perceptual interactions shape the time course of cueing

Performance in spatial cueing tasks is characterized by a rapid attentional enhancement with increasing cue–target SOA. We recently found that this enhancement function also applies when the cue and the target are presented invariably at a single central location, suggesting a universal cueing time course [Wilschut et al., 2011, PLoS ONE, 6, e27661]. However, using a very similar cueing task, Nieuwenstein et al. [2009, JoV, 9, 1–14] have found a rather different pattern, namely a U-shaped deficit in performance after a cue-like stimulus. The present study varied the properties of the cue and the target in order to investigate the mechanisms underlying the different time functions. In four experiments, cueing was found to either improve or decrease performance with increasing SOA, depending on the type of target that was used. In addition, the level of performance at the shortest cue–target intervals (33–83ms) was dependent on the relative strength of the cue and the target, akin to what has been found in visual masking studies. The results suggest that cueing shapes performance via two mechanisms, one sensory-related and one attention-related, the combination of which results in either U-shaped or monotonic patterns.

Inhibitory control and working memory in post-institutionalized children.

Inhibitory control and working memory were examined in post-institutionalized (PI) children adopted into United States families from Russian institutions. The PI sample originated from institutions that were less severely depriving than those represented in previous studies and approximated the level of psychosocial deprivation, which is characterized by adequate physical resources but a lack of consistent and responsive caregiving. PI children (N = 75; 29 male) ranged in age from 8-17years (M = 12.97; SD = 3.03) and were grouped according to whether they were adopted after 14months or before 9months. A non-adopted comparison group (N = 133; 65 male) ranged in age from 8-17years (M = 12.26; SD = 2.75). PI children adopted after 14months of age displayed poorer performance on the stop-signal and spatial span tasks relative to PI children adopted before 9months of age after controlling for age at assessment. The two PI groups did not differ in their performance on a spatial self-ordered search task. Older-adopted PI children also showed poorer spatial span task performance compared to non-adopted children, but younger-adopted PI children did not. Task performance was significantly associated with parent-rated hyperactive-impulsive behavior in everyday contexts. These findings suggest that exposure to prolonged early institutional deprivation may be linked with inhibitory control and working memory difficulties years after adoption.

Revisiting Geschwind's hypothesis on brain lateralisation: A functional MRI study of digit ratio (2D:4D) and sex interaction effects on spatial working memory

The Geschwind-Behan-Galaburda (GBG) hypothesis links cerebral lateralisation with prenatal testosterone exposure. Digit ratio measures in adults have been established as potential markers of foetal sex hormonal milieu. The aim of the study was to evaluate the sex-dependent interaction of digit ratio measures and cerebral lateralization as well as their neurohemodynamic correlates using functional MRI (fMRI). Digit ratio measures—ratio of index finger (2D) length to ring finger (4D) length (2D:4D) and difference between 2D:4D of two hands, i.e., right minus left (DR–L)—were calculated using high resolution digital images in 70 right-handed participants (42 men) based on reliable and valid method. fMRI was acquired during the performance of a spatial working memory task in a subset of 25 individuals (14 men), and analysed using Statistical Parametric Mapping 8 (SPM8) and the Laterality Index toolbox for SPM8. Men had significantly less bilateral 2D:4D than women. There was a significant negative correlation between right 2D:4D and 2-Back task accuracy (2BACC) in women. A significant sex-by-right 2D:4D interaction was observed in left parahippocampal gyrus activation. Additionally, sex-by-DR–L interaction was observed in left IPL activation. DR–L showed a significant positive correlation with the whole brain Laterality Index (LI), and LI, in turn, demonstrated a significant negative correlation with 2BACC. Our study observations suggest several novel sex-differential relationships between 2D:4D measures and fMRI activation during spatial working memory task performance. Given the pre-existing background data supporting digit ratio measures as putative indicator of prenatal sex hormonal milieu, our study findings add support to the Geschwind-Behan-Galaburda (GBG) hypothesis.

Litter size, age-related memory impairments, and microglial changes in rat dentate gyrus: Stereological analysis and three dimensional morphometry

It has been demonstrated that rat litter size affects the immune cell response, but it is not known whether the long-term effects aggravate age-related memory impairments or microglial-associated changes. To that end, we raised sedentary Wistar rats that were first suckled in small or large litters (6 or 12pups/dam, respectively), then separated into groups of 2–3 rats from the 21st post-natal day to study end. At 4months (young adult) or 23months (aged), all individual rats were submitted to spatial memory and object identity recognition tests, and then sacrificed. Brain sections were immunolabeled with anti-IBA-1 antibodies to selectively identify microglia/macrophages. Microglial morphological changes in the molecular layer of the dentate gyrus were estimated based on three-dimensional reconstructions. The cell number and laminar distribution in the dentate gyrus was estimated with the stereological optical fractionator method. We found that, compared to young rat groups, aged rats from large litters showed significant increases in the number of microglia in all layers of the dentate gyrus. Compared to the microglia in all other groups, microglia in aged individuals from large litters showed a significantly higher degree of tree volume expansion, branch base diameter thickening, and cell soma enlargement. These morphological changes were correlated with an increase in the number of microglia in the molecular layer. Young adult individuals from small litters exhibited preserved intact object identity recognition memory and all other groups showed reduced performance in both spatial and object identity recognition tasks. We found that, in large litters, brain development was, on average, associated with permanent changes in the innate immune system in the brain, with a significant impact on the microglial homeostasis of aged rats.

Impaired spatial memory performance in a rat model of neuropathic pain is associated with reduced hippocampus-prefrontal cortex connectivity.

Chronic pain patients commonly complain of working memory deficits, but the mechanisms and brain areas underlying this cognitive impairment remain elusive. The neuronal populations of the mPFC and dorsal CA1 (dCA1) are well known to form an interconnected neural circuit that is crucial for correct performance in spatial memory-dependent tasks. In this study, we investigated whether the functional connectivity between these two areas is affected by the onset of an animal model of peripheral neuropathic pain. To address this issue, we implanted two multichannel arrays of electrodes in the mPFC and dCA1 of rats and recorded the neuronal activity during a food-reinforced spatial working memory task in a reward-based alternate trajectory maze. Recordings were performed for 3 weeks, before and after the establishment of the spared nerve injury model of neuropathy. Our results show that the nerve lesion caused an impairment of working memory performance that is temporally associated with changes in the mPFC populational firing activity patterns when the animals navigated between decision points-when memory retention was most needed. Moreover, the activity of both recorded neuronal populations after the nerve injury increased their phase locking with respect to hippocampal theta rhythm. Finally, our data revealed that chronic pain reduces the overall amount of information flowing in the fronto-hippocampal circuit and induces the emergence of different oscillation patterns that are well correlated with the correct/incorrect performance of the animal on a trial-by-trial basis. The present results demonstrate that functional disturbances in the fronto-hippocampal connectivity are a relevant cause for pain-related working memory deficits.

Disruption of spatial task performance in anorexia nervosa.

In anorexia nervosa (AN), body distortions have been associated with parietal cortex (PC) dysfunction. The PC is the anatomical substrate for a supramodal reference framework involved in spatial orientation constancy. Here, we sought to evaluate spatial orientation constancy and the perception of body orientation in AN patients. In the present study, we investigated the effect of passive lateral body inclination on the visual and tactile subjective vertical (SV) and body Z-axis in 25 AN patients and 25 healthy controls. Subjects performed visual- and tactile-spatial judgments of axis orientations in an upright position and tilted 90° clockwise or counterclockwise. We observed a significant deviation of the tactile and visual SV towards the body (an A-effect) under tilted conditions, suggesting a multisensory impairment in spatial orientation. Deviation of the Z-axis in the direction of the tilt was also observed in the AN group. The greater A-effect in AN patients may reflect reduced interoceptive awareness and thus inadequate consideration of gravitational inflow. Furthermore, marked body weight loss could decrease the somatosensory inputs required for spatial orientation. Our study results suggest that spatial references are impaired in AN. This may be due to particular integration of visual, tactile and gravitational information (e.g. vestibular and proprioceptive cues) in the PC.

The effect of non-informative spatial sounds on haptic scene recognition

Previous studies found that performance in tactile or haptic spatial tasks improved when non-informative visual information was available, suggesting that vision provides a precise spatial frame to which tactile information is referred. Here, we explored whether another intrinsically spatial modality, audition, can also affect haptic recognition. In all experiments, blindfolded participants first learned a scene through touch and were subsequently required to recognise the scene. We found no effect on haptic performance when white noise stimuli were presented from specific locations Experiment 1. However, performance was significantly reduced by pure tone stimuli presented from the same locations Experiment 2, moreover, these tones disrupted recall but not encoding of the haptic scene Experiment 3. In Experiment 4, we found that spatial rather than non-spatial auditory information was required to affect haptic performance. Finally, in Experiment 5 we found no specific benefit for familiar sound cues over unfamiliar or no sounds on haptic spatial performance. Our findings suggest that, in contrast to vision, auditory information is unlikely to have sufficient spatial precision therefore disrupting the spatial representation of haptic information. Our results add to a growing body of evidence for multisensory influences in the perception of space.

Thalamic mediodorsal nucleus and its participation in spatial working memory processes: comparison with the prefrontal cortex.

Working memory is a dynamic neural system that includes processes for temporarily maintaining and processing information. Working memory plays a significant role in a variety of cognitive functions, such as thinking, reasoning, decision-making, and language comprehension. Although the prefrontal cortex (PFC) is known to play an important role in working memory, several lines of evidence indicate that the thalamic mediodorsal nucleus (MD) also participates in this process. While monkeys perform spatial working memory tasks, MD neurons exhibit directionally selective delay-period activity, which is considered to be a neural correlate for the temporary maintenance of information in PFC neurons. Studies have also shown that, while most MD neurons maintain prospective motor information, some maintain retrospective sensory information. Thus, the MD plays a greater role in prospective motor aspects of working memory processes than the PFC, which participates more in retrospective aspects. For the performance of spatial working memory tasks, the information provided by a sensory cue needs to be transformed into motor information to give an appropriate response. A population vector analysis using neural activities revealed that, although the transformation of sensory-to-motor information occurred during the delay period in both the PFC and the MD, PFC activities maintained sensory information until the late phase of the delay period, while MD activities initially represented sensory information but then started to represent motor information in the earlier phase of the delay period. These results indicate that long-range neural interactions supported by reciprocal connections between the MD and the PFC could play an important role in the transformation of maintained information in working memory processes.