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High-frequency repetitive transcranial magnetic stimulation (HF-rTMS) remains a promising strategy for neurorehabilitation. The stimulation intensity (SI) influences the after-effects observed. Here, we examined if single sessions of a HF-rTMS protocol, administered at different suprathreshold SI, can be safely administered to able-bodied (AB) individuals.Six right-handed men were included in this pilot study. HF-rTMS was delivered over the left M1, in 10 trains of 75 biphasic stimuli at 15 Hz, at 105 to 120% of the individual resting motor threshold (RMT). Participants and EMG were monitored to control for signs of spread of excitation and brief EMG burst (BEB) post-stimulation. TMS side-effects questionnaires and the numeric rating scale (NRS) were administered during each session. Additionally, we assessed CSE and motor performance changes with measures of resting (rMEP) and active (aMEP) motor evoked potential and grip strength and the Box and Block test (BBT) scores, respectively.Overall, the sessions were tolerated and feasible without any pain development. EMG analysis during HF-rTMS revealed increased BEB frequency with SI. Statistical models revealed an increase of CSE at rest (rMEP) but not during active muscle contraction (aMEP). No linear relationship was observed between HF-rTMS intensity and rMEP increase. No significant changes were highlighted for motor performance measures.Although feasible and tolerable by the AB tested, the results demonstrate that when administered at suprathreshold SI, 15 Hz-rTMS reveals signs of persistent excitation, suggesting that safety precautions and close monitoring of participants should be performed when testing such stimulation protocols.

Traumatic brain injury (TBI) often results in balance impairment, increasing the risk of falls, and the chances of further injuries. However, the underlying neural mechanisms of postural control after TBI are not well understood. To this end, we conducted a pilot study to explore the neural mechanisms of unpredictable balance perturbations in 17 chronic TBI participants and 15 matched healthy controls (HC) using the EEG, MRI, and diffusion tensor imaging (DTI) data. As quantitative measures of the functional integration and segregation of the brain networks during the postural task, we computed the global graph‐theoretic network measures (global efficiency and modularity) of brain functional connectivity derived from source‐space EEG in different frequency bands. We observed that the TBI group showed a lower balance performance as measured by the center of pressure displacement during the task, and the Berg Balance Scale (BBS). They also showed reduced brain activation and connectivity during the balance task. Furthermore, the decrease in brain network segregation in alpha‐band from baseline to task was smaller in TBI than HC. The DTI findings revealed widespread structural damage. In terms of the neural correlates, we observed a distinct role played by different frequency bands: theta‐band modularity during the task was negatively correlated with the BBS in the TBI group; lower beta‐band network connectivity was associated with the reduction in white matter structural integrity. Our future studies will focus on how postural training will modulate the functional brain networks in TBI., EEG connectivity graph measures were studied in traumatic brain injury (TBI) during the balance perturbation task. TBI group showed altered brain activation and connectivity during the balance task. Graph‐theoretic measures showed that the task modulation of brain network segregation in alpha‐band was reduced in TBI and the network segregation in theta‐band was associated with postural instability in TBI.

Objective of the study: This study aimed at characterizing output features of the higher-order motor control centers (hoMCCs), including secondary (premotor cortex [Pre] and supplementary motor area [SMA]) and association (prefrontal cortex [PFC]) motor regions to the primary motor cortex (M1) during graded force tasks. It is well known that one of the major roles of the primary motor cortex (M1) is controlling motor output such as muscle force. However, it is unclear how the hoMCCs interact with M1 in regulating voluntary muscle contractions. Methods: fMRI data was acquired during graded force tasks and fMRI-based effective connectivity (EC) and muscle force analyses were performed to study the relationship between hoMCCs-M1 effective connectivity and voluntarily exerted handgrip force. Results: The results show that there is a consistent information flow from the hoMCCs to M1 under all force conditions, suggesting a hierarchical control mechanism in the brain in regulating voluntary muscle force. Only the premotor cortex exhibited a significant role in mediating the level of force production through its EC with M1 but that role diminished when the exerted force was high, suggesting perhaps a ceiling and/or fatigue effect on the EC. A flip in the direction of EC from the primary sensory cortex (S1) to the hoMCCs (PFC, SMA, and Pre) at lower force levels while at higher forces EC was observed from the hoMCCs to S1. Conclusion: The hoMCCs regulate M1 output to produce desired voluntary muscle force. Only the Pre-to-M1 connectivity strength directly correlates with the force level especially from low to moderate levels. The hoMCCs are involved in modulating higher force production likely by strengthening M1 output and downgrading inhibition from S1 to M1.

The neurophysiological mechanism of cancer-related fatigue (CRF) remains poorly understood. EEG was examined during a sustained submaximal contraction (SC) task to further understand our prior research findings of greater central contribution to early fatigue during SC in CRF. Advanced cancer patients and matched healthy controls performed an elbow flexor SC until task failure while undergoing neuromuscular testing and EEG recording. EEG power changes over left and right sensorimotor cortices were analyzed and correlated with brief fatigue inventory (BFI) score and evoked muscle force, a measure of central fatigue. Brain electrical activity changes during the SC differed in CRF from healthy subjects mainly in the theta (4-8 Hz) and beta (12-30 Hz) bands in the contralateral (to the fatigued limb) hemisphere; changes were correlated with the evoked force. Also, the gamma band (30-50 Hz) power decrease during the SC did not return to baseline after 2 min of rest in CRF, an effect correlated with BFI score. In conclusion, altered brain electrical activity during a fatigue task in patients is associated with central fatigue during SC or fatigue symptoms, suggesting its potential contribution to CRF during motor performance. This information should guide the development and use of rehabilitative interventions that target the central nervous system to maximize function recovery.

Balance impairment or the loss of balance control is one of the most debilitating consequences of Traumatic Brain Injury (TBI). The levels of balance impairment may not be necessarily associated with the severity level of TBI, which makes it more difficult to do the correlational analysis of the balance impairment and its neural underpinnings. Therefore, we conducted a study where we collected the neurophysiological data (EEG and EMG) during a balance control task on a computerized posturography platform in a group of 17 TBIs and 15 age-matched healthy controls. Further, to distinguish balance-impaired TBIs (BI-TBI) from non-impaired TBIs (BN-TBI), we stratified the level of balance impairment using the Berg Balance Scale, a functional outcome measure widely used in both research and clinical settings. We computed the brain functional connectivity features between different cortical regions of interest using the imaginary part of coherence in different frequency bands. These features are then studied in a mean-centered Partial Least Squares Correlation analysis, which is a data-driven framework with the advantage of handling more features than the number of samples, thus making it suitable for a small-sample study. Based on the nonparametric significance testing using permutation and bootstrap procedure, we noticed that theta-band connectivity strength in the following ROIs significantly contributed to distinguishing balance impaired from non-impaired population: left middle frontal gyrus, right precuneus, right precentral gyrus, bilateral middle occipital gyrus, right middle temporal gyrus, left superior frontal gyrus, left post-central gyrus, right paracentral lobule. The knowledge of specific neural regions associated with balance impairment helps better understand neural mechanisms of TBI-associated balance dysfunction and may guide the development of novel therapeutic strategies, including targeted noninvasive brain stimulation. Our future studies will investigate the effects of balance platform training on sensorimotor connectivity.

Conventional therapy improves motor recovery after stroke. However, 50% of stroke survivors still suffer from a significant level of long-term upper extremity impairment. Identifying a specific biomarker whose magnitude scales with the level of force could help in the development of more effective, novel, highly targeted rehabilitation therapies such as brain stimulation or neurofeedback. Four chronic stroke participants were enrolled in this pilot study to find such a neural marker using an Independent Component Analysis (ICA)-based source analysis approach, and investigate how it has been affected by the injury. Beta band desynchronization in the ipsilesional primary motor cortex was found to be most robustly scaling with force. This activity modulation with force was found to be significantly reduced, and to plateau at higher force than that of the contralesional (unaffected) side. A rehabilitation therapy that would target such a neuromarker could have the potential to strengthen the brain-to-muscle drive and improve motor learning and recovery.Clinical Relevance- This study identifies a neural marker that scales with motor output and shows how this modulation has been affected by stroke.

Repeatedly performing a submaximal motor task for a prolonged period of time leads to muscle fatigue manifested by its reduced capacity to generate force or power. Fatigue resulted from voluntary muscle contractions comprises a central and peripheral component, which demands a gradually increasing effort to perform the task as time elapses. However, we still lack a complete understanding of brain contribution to the enhancement of effort to cope with progressing fatigue because of repeated submaximal muscle contractions. The knowledge of how muscle fatigue modulates brain activities in a healthy population will help rationalize why certain patients experience exacerbated fatigue while carrying out mundane tasks. The intermittent motor tasks closely resemble many activities of daily living (ADL), thus remaining physiologically relevant to study fatigue. The scope of this study is therefore to investigate the EEG-based brain activation patterns in healthy subjects performing intermittent submaximal muscle contractions until self-perceived exhaustion. Fourteen participants (median age 51.5 years; age range 26-72 years; 5 males) repeated elbow flexion contractions at 40% maximum voluntary contraction by following visual cues displayed on an oscilloscope screen until subjective exhaustion. Each contraction lasted ~5 s with a 2-s rest between trials. The force, EEG, and surface EMG (from elbow joint muscles) data were simultaneously collected. After preprocessing, we selected a subset of trials at the beginning, middle, and end of the study session representing brain activities germane to mild, moderate, and severe fatigue conditions, respectively, to compare and contrast the changes in the EEG time-frequency (TF) characteristics across the conditions. The TF analyses were conducted both at the channel and source level. The outcome of the channel- and source-level analyses reveal that the theta, alpha, and beta power spectral densities (PSDs) vary in proportion to fatigue levels in cortical motor areas. Importantly, the pairwise PSD differences between the fatigue conditions survived the statistical inferential tests with a p-value threshold of 0.05. We observed a statistically significant change in the band-specific spectral power in relation to the graded fatigue from both the steady- and post- contraction EEG data. The findings would enhance our understanding of the etiology and physiology of voluntary motor action-related fatigue and provide pointers to counteract the perception of muscle weakness and lack of motor endurance associated with ADL. The study outcome would help evaluate how clinical conditions such as neurological disorders and cancer treatment alter neural mechanisms underlying fatigue in future studies and develop therapeutic strategies for restoring the patients9 ability to participate in ADL by mitigating central and muscle fatigue.

Background: Persistent post-mastectomy pain (PPMP) is common after surgery. Although multiple modalities have been used to treat this type of pain, including physical medicine, physical therapy and interventional approaches, managing PPMP may be still a challenge for breast cancer survivors. Currently, serratus plane block (SPB) as a novel regional anesthetic technique shows promising results for controlling chronic pain. Methods: We report four cases of patients with PPMP that were performed using superficial serratus plane block (SSPB) at our clinic. A retrospective review of effect of pain relief was collected through postprocedure interviews.Results: We found that two of our patients were successfully treated with SSPB for pain after treatment for breast cancer. The third patient had an intercostobrachial nerve block that produced incomplete pain relief, but had adequate pain relief with a SSPB. However, the fourth patient reported no pain relief after SSPB.Conclusion: These cases illustrate that the patients with PPMP could benefit from SSPB. Particularly, we find patients with a subjective sense of “tightness” relating to reconstructive surgeries may be a good candidate for SSPB. Further studies are warranted to evaluate this block for PPMP, as it is low risk and relatively simple to perform.

Persons with upper extremity (UE) impairments due to spinal cord injury (SCI) have limited capacity to move or perform basic activities of daily living (ADL). Such movement limitations significantly reduce a patient’s quality of life (QOL) and level of independence. Restoration of UE motor function in people with SCI remains a high priority in rehabilitation and in the field of assistive technology. UE myoelectric powered wearable orthoses (UE-MPWO) specifically designed to restore wrist/hand movements may help fill the gap by increasing strength of the participating muscles, range of motion (ROM) of the joints, and ability to perform daily tasks involving using wrist/hand in persons with SCI. The goal of this study was to evaluate the effects of the UE-MPWO (MyoPro) in ameliorating wrist/hand/UE movement capability, and increasing ADL and QOL in people with SCI.

Background and Purpose. Cancer-related fatigue (CRF) is widely recognized as one of the most common symptoms and side effects of cancer and/or its treatment. However, neuropathological mechanisms contributing to CRF are largely unknown, and the lack of knowledge makes CRF difficult to treat. Recent research has shown dissociation between changes in the brain and muscle signals during voluntary motor performance in cancer survivors with CRF, and this dissociation may be caused by an interruption in functional coupling (FC) of the two signals. The goal of this study was to assess the FC between EEG (cortical signal) and EMG (muscular signal) in individuals with CRF and compare the FC with that of healthy controls during a motor task that led to progressive muscle fatigue. Method. Eight cancer survivors with CRF and nine healthy participants sustained an isometric elbow flexion contraction (at 30% maximal level) until self-perceived exhaustion. The entire duration of the EEG and EMG recordings was divided into the first-half (less-fatigue stage) and second-half (more-fatigue stage) artifact-free epochs without overlapping. The EEG-EMG coupling (measured by coherence of the two signals) in each group and stage was computed. Coherence values at different frequencies were statistically analyzed using a repeated-measure general linear model. Results. The results demonstrated that compared to healthy controls, CRF participants sustained the contraction for a significantly shorter time and exhibited robust and significantly lower EEG-EMG coherence at the alpha (8~14 Hz) and beta (15~35 Hz) frequency bands. Both the CRF and healthy control groups exhibited significantly decreased EEG-EMG coherence from the less-fatigue to more-fatigue stages at the alpha and beta frequency bands, indicating fatigue-induced weakening of functional corticomuscular coupling. Conclusion. Impaired functional coupling between the brain and muscle signals could be a consequence of cancer and/or its treatment, and it may be one of the contributing factors to the abnormal feeling of fatigue that caused the early failure of sustaining a prolonged motor task.

Spatial neglect after right brain stroke affects balance, and improvements in sitting balance after prism adaptation have been demonstrated using short-duration center of pressure (CoP) data. We present long-duration (5 min) CoP and trunk muscles electromyography recordings of a 61-year-old man with left-sided spatial neglect, before and after a single session of prism adaptation. His CoP-derived measures showed improved balance and postural stability in both the anterior-posterior and medial-lateral directions after prism adaptation. Concurrently, asymmetry in neuromuscular activations was reduced. The findings suggest that improved sitting balance may be associated with more symmetrical activation of trunk muscles after prism adaptation.

this study examines the relationship between brain structural connectivity, and physical and cognitive performances in individuals with Traumatic Brain Injury (TBI). Nine moderate to severe TBI participants were included in the study, and regression analysis was performed to explore if DTI connectivity of 16 regions of interest can predict individuals' : 1) Maximum Voluntary Contraction (MVC), 2) time component of Wolf Motor Function Test (WMFT), 3) Reaction Time (RT) during bimanual force matching task, 4) Performance Error Measurement (PEM) during bimanual force matching task, and 5) cognitive assessment of task switching using Trail Making (TM) test. Results showed that slower WMFT, PEM, and TM can be predicted by weaker cerebrospinal tract connectivity. Higher Caudate connectivity predicted higher WMFT and slower RT, and higher right Cingulum predicted faster TM. Current results suggest that measures of cognitive-motor interference may be better indicators of functional performance than single cognitive and motor performance tests.

Traumatic brain injury (TBI) is the main cause of disability in people younger than 35 in the United States. The mechanisms of TBI are complex resulting in both focal and diffuse brain damage. Fractal dimension (FD) is a measure that can characterize morphometric complexity and variability of brain structure especially white matter (WM) structure and may provide novel insights into the injuries evident following TBI. FD-based brain morphometry may provide information on WM structural changes after TBI that is more sensitive to subtle structural changes post injury compared to conventional MRI measurements. Anatomical and diffusion tensor imaging (DTI) data were obtained using a 3 T MRI scanner in subjects with moderate to severe TBI and in healthy controls (HC). Whole brain WM volume, grey matter volume, cortical thickness, cortical area, FD and DTI metrics were evaluated globally and for the left and right hemispheres separately. A neuropsychological test battery sensitive to cognitive impairment associated with traumatic brain injury was performed. TBI group showed lower structural complexity (FD) bilaterally (p

Background Co-occurring mobility and cognitive impairments are common, debilitating, and poorly-managed with pharmacological therapies in persons with multiple sclerosis (MS). Exercise rehabilitation (ER), particularly walking ER, has been suggested as one of the best approaches for managing these manifestations of MS. However, there is a focal lack of efficacy of ER on mobility and cognitive outcomes in persons with MS who present with substantial neurological disability. Such severe neurological disability oftentimes precludes the ability for participation in highly-intensive and repetitive ER that is necessary for eliciting adaptations in mobility and cognition. To address such a concern, robotic exoskeleton-assisted ER (REAER) might represent a promising intervention approach for managing co-occurring mobility and cognitive impairments in those with substantial MS disability who might not benefit from traditional ER. Methods The current pilot single-blind, randomized controlled trial (RCT) compared the effects of 4-weeks of REAER with 4-weeks of conventional gait training (CGT) as a standard-of-care control condition on functional mobility (timed up-and-go; TUG), walking endurance (six-minute walk test; 6MWT), cognitive processing speed (CPS; Symbol Digit Modalities Test; SDMT), and brain connectivity (thalamocortical resting-state functional connectivity (RSFC) based on fMRI) outcomes in 10 persons with substantial MS-related neurological disability. Results Overall, compared with CGT, 4-weeks of REAER was associated with large improvements in functional mobility (ηp2=.38), CPS (ηp2=.53), and RSFC between the thalamus and ventromedial prefrontal cortex (ηp2=.72), but not walking endurance (ηp2=.01). Further, changes in RSFC were moderately associated with changes in TUG, 6MWT, and SDMT performance, respectively, whereby increased thalamocortical RSFC was associated with improved functional mobility, walking endurance, and CPS (|ρ|>.36). Conclusion The current pilot RCT provides initial support for REAER as an approach for improving functional mobility and CPS, perhaps based on adaptive and integrative central nervous system plasticity, namely increases in RSFC between the thalamus and ventromedial prefrontal cortex, in a small sample of persons with substantial MS disability. Such a pilot trial provides proof-of-concept data for the design and implementation of an appropriately-powered RCT of REAER in a larger sample of persons with MS who present with co-occurring impairments in both mobility and cognitive functioning.

Fractal dimension (FD) is a quantitative parameter that can characterizes the complexity of human brain tissue. Extensive grey matter (GM) pathology has been previously identified in Frontotemporal dementia (FTD) and its variants. The aim of the present study was to investigate the GM morphometric abnormalities in the behavioral variant FTD (bvFTD) and primary progressive aphasia (PPA) using FD analysis. Twenty-seven bvFTD, 12 PPA and 20 controls were studied. SPM8 was used to segment the brain into GM tissue. Then the FD values were estimated for the GM skeleton, surface and general structure in patients and controls using our previously published algorithm. We found that patients with bvFTD had significant reduction in FD values of skeleton and general structure when compared to controls. In PPA, more significant decrease in FD was noted in the whole brain and left hemisphere skeleton along with left hemisphere general structure. Only the right hemisphere skeleton had a significant correlation with total score of Frontal Systems Behavior Scale (FrSBe). The results showed that the variants of FTD are associated with disease specific morphometric complexity patterns. These results indicate that FD can be used as a biomarker for the structural changes associated with neurodegenerative diseases.

30-60% of traumatic brain injury (TBI) patients suffer from long-term balance deficit. Even though motor preparation and execution are altered and slowed in TBI, their relative contribution and importance to posture instability remain poorly understood. This study investigates the impaired cortical dynamics and neuromuscular response in TBI in response to balance perturbation and its relation to balance deficit. 12 TBI and 6 healthy control (HC) participants took the Berg Balance Scale (BBS) test and participated in a balance perturbation task where they were subjected to random anterior/posterior translation, while brain (EEG), muscle (EMG) activities, and center of pressure (COP) were continuously recorded. Using independent component analysis (ICA), the component most responsible for the N1 component of the perturbation evoked potential (PEP) was selected and its amplitude and latency were extracted. Balance task performance was measured by computing the COP displacement during the task. TBI had a significantly lower BBS, larger COP displacement and lower N1 amplitude compared to the HC group. No group differences was found for N1 latency and muscle activity onset delay to the perturbation. BBS was correlated with the COP displacement and N1 amplitude, and COP displacement was correlated with N1 latency. TBI balance deficit may be associated with more impaired than delayed cortical response to balance perturbation.

The overall goal of this study is to investigate the role of parietal cortex in the control of walking in persons with Multiple Sclerosis (pwMS). We examined within-brain connectivity and cortico-muscular connectivity as pwMS and healthy control (HC) participants walked on an instrumented treadmill. Cortical activity was collected using EEG, muscle activity was collected using wireless EMG modules, and gait data were obtained by using the instrumented treadmill. Results show significant activation of sensorimotor and posterior parietal cortex during walking in both groups. Connectivity between parietal (posterior cingulate cortex PCC) and premotor regions (pars opercularis), and between PCC and contralateral muscles were higher in the healthy control group. Higher connectivity correlated with higher walking speed.

Multiple sclerosis (MS) is a non-traumatic, immune-mediated neurodegenerative disease of the central nervous system (CNS), affecting more than 2 million individuals globally and approximately one million in the United States [1], [2]. This autoimmune inflammatory disease of the CNS featuring both neuroinflammatory and neurodegenerative aspects [3], often results in mobility and cognitive impairment. Rehabilitation has been suggested as the best [4], and perhaps, one of few methods for restoring function in MS [5]. The goal of the present investigation is to examine the effects of 4 weeks of supervised, over-ground gait training using a robotic exoskeleton (RE) compared with a control condition (conventional gait therapy, CGT) in persons with MS with ambulatory and cognition disabilities. Four subjects (mean age=50 years, three females) with relapsing-remitting MS (RRMS) participated in this study and completed a total of eight sessions (1-hour/session) gait training in a standard therapy gym either using a RE supervised by an RE training physical therapist (PT) or with the CGT supervised by a PT. Outcome measures (walking speed and temporal-spatial parameters) were measured on a level surface without RE using an instrumented walkway, for both groups, pre- and post-intervention. The two participants in the RE group were also tested in the same testing environment, while wearing a RE pre- and post-intervention. Cognitive processing speed was assessed using the Symbol Digit Modalities Test (SDMT) pre- and post-intervention. Subjects in the RE group tested without a RE increased average walking speed, stride length, and step length with decreased stride width and step time bilaterally after the 8-session of RE training. The two participants in the CGT group only had modest improvements in walking performance. Furthermore, while the CGT group had no improvements in the processing speed (SDMT scores), an average of 80% improvement in the processing speed was noted in the RE group.

It is well known that corticomotor excitability is altered during the post-exercise depression following fatigue within the primary motor cortex (M1). However, it is currently unknown whether corticomotor reorganization following muscle fatigue differs between magnitudes of force and whether corticomotor reorganization occurs measured with transcranial magnetic stimulation. Fifteen young healthy adults (age 23.8±1.4, 8 females) participated in a within-subjects, repeated measures design study, where they underwent three testing sessions separated by one-week each. Subjects performed separate sessions of each: low-force isometric contraction (30% maximal voluntary contraction [MVC]), high-force isometric contraction (95% MVC) of the first dorsal interosseous (FDI) muscle until self-perceived exhaustion, as well as one session of 30 minutes rest as a control. We examined changes in corticomotor map area, excitability and location of the FDI representation in and around M1 using transcranial magnetic stimulation. The main finding was that following low-force, but not high-force fatigue corticomotor map area and excitability reduced [by 3cm(2) (t (14) =−2.94, p=0.01) and 56% respectively t(14) =−4.01, p < 0.001)]. Additionally, the region of corticomotor excitability shifted posteriorly (6.4±2.5mm) (t(14) = −6.33, p = .019). Corticomotor output became less excitable particularly in regions adjoining M1. Overall, post-exercise depression is present in low-force, but not for high-force fatigue. Further, low-force fatigue results in a posterior shift in corticomotor output. These changes may be indicative of increased sensory feedback from the somatosensory cortex during the recovery phase of fatigue.

The human visual system is highly sensitive to biological motion. Even when a point-light walker is temporarily occluded from view by other objects, our eyes are still able to maintain tracking continuity. To investigate how the visual system establishes a correspondence between the biological-motion stimuli visible before and after the disruption, we used the occlusion paradigm with biological-motion stimuli that were intact or scrambled. The results showed that during visually guided tracking, both the observers' predicted times and predictive smooth pursuit were more accurate for upright biological motion (intact and scrambled) than for inverted biological motion. During memory-guided tracking, however, the processing advantage for upright as compared with inverted biological motion was not found in the scrambled condition, but in the intact condition only. This suggests that spatial location information alone is not sufficient to build and maintain the representational continuity of the biological motion across the occlusion, and that the object identity may act as an important information source in visual tracking. The inversion effect disappeared when the scrambled biological motion was occluded, which indicates that when biological motion is temporarily occluded and there is a complete absence of visual feedback signals, an oculomotor prediction is executed to maintain the tracking continuity, which is established not only by updating the target's spatial location, but also by the retrieval of identity information stored in long-term memory.