Motor speech disorders, including apraxia of speech (AOS), account for over 50% of the communicat... more Motor speech disorders, including apraxia of speech (AOS), account for over 50% of the communication disorders following stroke. Given its prevalence and impact, and the need to understand its neural mechanisms, we used resting state functional MRI to examine functional connectivity within a network of regions previously hypothesized as being associated with AOS (bilateral anterior insula (aINS), inferior frontal gyrus (IFG), and ventral premotor cortex (PM)) in a group of 32 left hemisphere stroke patients and 18 healthy, age-matched controls. Two expert clinicians rated severity of AOS, dysarthria and nonverbal oral apraxia of the patients. Fifteen individuals were categorized as AOS and 17 were AOS-absent. Comparison of connectivity in patients with and without AOS demonstrated that AOS patients had reduced connectivity between bilateral PM, and this reduction correlated with the severity of AOS impairment. In addition, AOS patients had negative connectivity between the left PM and right aINS and this effect decreased with increasing severity of non-verbal oral apraxia. These results highlight left PM involvement in AOS, begin to differentiate its neural mechanisms from those of other motor impairments following stroke, and help inform us of the neural mechanisms driving differences in speech motor planning and programming impairment following stroke.
This study examined 30 young and 10 elderly subjects to test whether orienting of attention could... more This study examined 30 young and 10 elderly subjects to test whether orienting of attention could be measured in audition. Orienting in a mixed-modal condition in which stimuli were either auditory or visual was also tested. The dependent measure was the reaction time (RT) to lateralized targets when the locations were predicted by antecedent arrow cues that were correct (valid), were incorrect (invalid), or provided no lateralizing information (neutral). A comparison between the two groups among the different conditions showed that elderly subjects had longer RTs than the younger participants, but the pattern of results was similar in both groups. In addition, a similar RT pattern was found for each modal condition: Valid trials elicited the fastest responses and invalid trials the slowest. These findings suggest that the mechanisms involved in orienting attention operate in audition and that individuals may allocate their processing resources among multiple sensory pools. Moreover...
Over 90 percent of patients with Parkinson's disease experience speech-motor impairment, name... more Over 90 percent of patients with Parkinson's disease experience speech-motor impairment, namely, hypokinetic dysarthria characterized by reduced pitch and loudness. Resting-state functional connectivity analysis of blood oxygen level-dependent functional magnetic resonance imaging is a useful measure of intrinsic neural functioning. We utilized resting-state functional connectivity modeling to analyze the intrinsic connectivity in patients with Parkinson's disease within a vocalization network defined by a previous meta-analysis of speech (Brown et al., 2009). Functional connectivity of this network was assessed in 56 patients with Parkinson's disease and 56 gender-, age-, and movement-matched healthy controls. We also had item 5 and 18 of the UPDRS, and the PDQ-39 Communication subscale available for correlation with the voice network connectivity strength in patients. The within-group analyses of connectivity patterns demonstrated a lack of subcortical-cortical connect...
Methods: We studied 19 adults with PDS, and 21 HC matched for age, sex, education and hand prefer... more Methods: We studied 19 adults with PDS, and 21 HC matched for age, sex, education and hand preference. Participants with PDS were assessed employing self-report, clinical PDS diagnosis before age 8, and the diagnosis was confirmed for experts after assess 3 ...
Finger tapping sequences are a commonly used measure of motor learning in functional imaging stud... more Finger tapping sequences are a commonly used measure of motor learning in functional imaging studies. Subjects repeat a defined sequence of finger taps as fast as possible for a set period of time. The number of sequences completed per unit time is the measure of performance. Assessment of speed and accuracy is generally accomplished by video recording the session then replaying in slow motion to assess rate and accuracy. This is a time consuming and error prone process. Keyboards and instrumented gloves have also been used for task assessment though they are relatively expensive and not usually compatible in a magnetic resonance imaging (MRI) scanner. To address these problems, we developed a low cost system using MRI compatible force sensitive resistors (FSR) to assess the performance during a finger sequence task. This system additionally provides information on finger coordination including time between sequences, intervals between taps, and tap duration. The method was validated by comparing the FSR system results with results obtained by video analysis during the same session.
Recent years have seen a growing debate concerning the function of the cerebellum. We have propos... more Recent years have seen a growing debate concerning the function of the cerebellum. We have proposed that the cerebellum may be more involved in sensory than motor function, and have specifically predicted that its activity should be particularly enhanced during sensory discrimination tasks. Consistent with this hypothesis we have previously shown using functional Magnetic Resonance Imaging (fMRI) that 'finger' regions of the human cerebellum are more active during tactile discrimination tasks than during finger movement alone . In this report we extend our investigation to the auditory system using PET. Auditory studies remove the confound of movement inherent in studies of other sensory systems, including the somatosensory system. Two previous PET studies have shown patterns of cerebellar activations associated to the discrimination of sound intensity and duration . Here we test our hypothesis using a pitch discrimination task.
Many service members and veterans report chronic unexplained symptoms such as pain, fatigue and m... more Many service members and veterans report chronic unexplained symptoms such as pain, fatigue and memory complaints, which have most recently been characterized as post-deployment syndrome (PDS). Chronic widespread pain is a component of this syndrome, producing significant disability and considerable health care costs. The similarity between the nature of these complaints and other medically unexplained illnesses such as fibromyalgia, irritable bowel syndrome, and chronic fatigue syndrome suggest that they may share a common mechanism. Here, we provide support for PDS as a consequence of pain and sensory amplification secondary to neuroplastic changes within the central nervous system, a phenomenon often termed central sensitization. We also discuss how factors such as stress and genetics may promote chronic widespread pain in veterans and service members who develop PDS.
Our goal was to prospectively study the course of oppositional defiant disorder (ODD) symptomatol... more Our goal was to prospectively study the course of oppositional defiant disorder (ODD) symptomatology in children and adolescents in the first 2 years after traumatic brain injury (TBI). Fifty children aged 6 to 14, hospitalized after TBI, were assessed soon after TBI regarding injury severity; preinjury psychiatric, socioeconomic, family functioning, and family psychiatric history status; and neuroimaging was analyzed. ODD symptomatology in the first year after TBI was related to preinjury family function, social class, and preinjury ODD symptomatology. Increased severity of TBI predicted ODD symptomatology 2 years after injury. Change (from before TBI) in ODD symptomatology at 6, 12, and 24 months after TBI was influenced by socioeconomic status. Only at 2 years after injury was severity of injury a predictor of change in ODD symptomatology. The influence of psychosocial factors appears greater than severity of injury in accounting for ODD symptomatology and change in such symptomatology in the first but not the second year after TBI in children and adolescents. This appears related to persistence of new ODD symptomatology after more serious TBI.
We explored relationships between decline in cognitive processing speed (CPS) and change in front... more We explored relationships between decline in cognitive processing speed (CPS) and change in frontal lobe MRI/MRS-based indices of cerebral integrity in 38 healthy adults (age 57-90 years). CPS was assessed using a battery of four timed neuropsychological tests: Grooved Pegboard, Coding, Symbol Digit Modalities Test and Category Fluency (Fruits and Furniture). The neuropsychological tests were factor analyzed to extract two components of CPS: psychomotor (PM) and psychophysical (PP). MRI-based indices of cerebral integrity included three cortical measurements per hemisphere (GM thickness, intergyral and sulcal spans) and two subcortical indices (fractional anisotropy (FA), measured using track-based spatial statistics (TBSS), and the volume of hyperintense WM (HWM)). MRS indices included levels of choline-containing compounds (GPC + PC), phosphocreatine plus creatine (PCr + Cr), and N-acetylaspartate (NAA), measured bilaterally in the frontal WM bundles. A substantial fraction of the variance in the PM-CPS (58%) was attributed to atrophic changes in frontal WM, observed as increases in sulcal span, declines in FA values and reductions in concentrations of NAA and choline-containing compounds. A smaller proportion (20%) of variance in the PP-CPS could be explained by bilateral increases in frontal sulcal span and increases in HWM volumes.
Motor speech disorders, including apraxia of speech (AOS), account for over 50% of the communicat... more Motor speech disorders, including apraxia of speech (AOS), account for over 50% of the communication disorders following stroke. Given its prevalence and impact, and the need to understand its neural mechanisms, we used resting state functional MRI to examine functional connectivity within a network of regions previously hypothesized as being associated with AOS (bilateral anterior insula (aINS), inferior frontal gyrus (IFG), and ventral premotor cortex (PM)) in a group of 32 left hemisphere stroke patients and 18 healthy, age-matched controls. Two expert clinicians rated severity of AOS, dysarthria and nonverbal oral apraxia of the patients. Fifteen individuals were categorized as AOS and 17 were AOS-absent. Comparison of connectivity in patients with and without AOS demonstrated that AOS patients had reduced connectivity between bilateral PM, and this reduction correlated with the severity of AOS impairment. In addition, AOS patients had negative connectivity between the left PM and right aINS and this effect decreased with increasing severity of non-verbal oral apraxia. These results highlight left PM involvement in AOS, begin to differentiate its neural mechanisms from those of other motor impairments following stroke, and help inform us of the neural mechanisms driving differences in speech motor planning and programming impairment following stroke.
This study examined 30 young and 10 elderly subjects to test whether orienting of attention could... more This study examined 30 young and 10 elderly subjects to test whether orienting of attention could be measured in audition. Orienting in a mixed-modal condition in which stimuli were either auditory or visual was also tested. The dependent measure was the reaction time (RT) to lateralized targets when the locations were predicted by antecedent arrow cues that were correct (valid), were incorrect (invalid), or provided no lateralizing information (neutral). A comparison between the two groups among the different conditions showed that elderly subjects had longer RTs than the younger participants, but the pattern of results was similar in both groups. In addition, a similar RT pattern was found for each modal condition: Valid trials elicited the fastest responses and invalid trials the slowest. These findings suggest that the mechanisms involved in orienting attention operate in audition and that individuals may allocate their processing resources among multiple sensory pools. Moreover...
Over 90 percent of patients with Parkinson's disease experience speech-motor impairment, name... more Over 90 percent of patients with Parkinson's disease experience speech-motor impairment, namely, hypokinetic dysarthria characterized by reduced pitch and loudness. Resting-state functional connectivity analysis of blood oxygen level-dependent functional magnetic resonance imaging is a useful measure of intrinsic neural functioning. We utilized resting-state functional connectivity modeling to analyze the intrinsic connectivity in patients with Parkinson's disease within a vocalization network defined by a previous meta-analysis of speech (Brown et al., 2009). Functional connectivity of this network was assessed in 56 patients with Parkinson's disease and 56 gender-, age-, and movement-matched healthy controls. We also had item 5 and 18 of the UPDRS, and the PDQ-39 Communication subscale available for correlation with the voice network connectivity strength in patients. The within-group analyses of connectivity patterns demonstrated a lack of subcortical-cortical connect...
Methods: We studied 19 adults with PDS, and 21 HC matched for age, sex, education and hand prefer... more Methods: We studied 19 adults with PDS, and 21 HC matched for age, sex, education and hand preference. Participants with PDS were assessed employing self-report, clinical PDS diagnosis before age 8, and the diagnosis was confirmed for experts after assess 3 ...
Finger tapping sequences are a commonly used measure of motor learning in functional imaging stud... more Finger tapping sequences are a commonly used measure of motor learning in functional imaging studies. Subjects repeat a defined sequence of finger taps as fast as possible for a set period of time. The number of sequences completed per unit time is the measure of performance. Assessment of speed and accuracy is generally accomplished by video recording the session then replaying in slow motion to assess rate and accuracy. This is a time consuming and error prone process. Keyboards and instrumented gloves have also been used for task assessment though they are relatively expensive and not usually compatible in a magnetic resonance imaging (MRI) scanner. To address these problems, we developed a low cost system using MRI compatible force sensitive resistors (FSR) to assess the performance during a finger sequence task. This system additionally provides information on finger coordination including time between sequences, intervals between taps, and tap duration. The method was validated by comparing the FSR system results with results obtained by video analysis during the same session.
Recent years have seen a growing debate concerning the function of the cerebellum. We have propos... more Recent years have seen a growing debate concerning the function of the cerebellum. We have proposed that the cerebellum may be more involved in sensory than motor function, and have specifically predicted that its activity should be particularly enhanced during sensory discrimination tasks. Consistent with this hypothesis we have previously shown using functional Magnetic Resonance Imaging (fMRI) that 'finger' regions of the human cerebellum are more active during tactile discrimination tasks than during finger movement alone . In this report we extend our investigation to the auditory system using PET. Auditory studies remove the confound of movement inherent in studies of other sensory systems, including the somatosensory system. Two previous PET studies have shown patterns of cerebellar activations associated to the discrimination of sound intensity and duration . Here we test our hypothesis using a pitch discrimination task.
Many service members and veterans report chronic unexplained symptoms such as pain, fatigue and m... more Many service members and veterans report chronic unexplained symptoms such as pain, fatigue and memory complaints, which have most recently been characterized as post-deployment syndrome (PDS). Chronic widespread pain is a component of this syndrome, producing significant disability and considerable health care costs. The similarity between the nature of these complaints and other medically unexplained illnesses such as fibromyalgia, irritable bowel syndrome, and chronic fatigue syndrome suggest that they may share a common mechanism. Here, we provide support for PDS as a consequence of pain and sensory amplification secondary to neuroplastic changes within the central nervous system, a phenomenon often termed central sensitization. We also discuss how factors such as stress and genetics may promote chronic widespread pain in veterans and service members who develop PDS.
Our goal was to prospectively study the course of oppositional defiant disorder (ODD) symptomatol... more Our goal was to prospectively study the course of oppositional defiant disorder (ODD) symptomatology in children and adolescents in the first 2 years after traumatic brain injury (TBI). Fifty children aged 6 to 14, hospitalized after TBI, were assessed soon after TBI regarding injury severity; preinjury psychiatric, socioeconomic, family functioning, and family psychiatric history status; and neuroimaging was analyzed. ODD symptomatology in the first year after TBI was related to preinjury family function, social class, and preinjury ODD symptomatology. Increased severity of TBI predicted ODD symptomatology 2 years after injury. Change (from before TBI) in ODD symptomatology at 6, 12, and 24 months after TBI was influenced by socioeconomic status. Only at 2 years after injury was severity of injury a predictor of change in ODD symptomatology. The influence of psychosocial factors appears greater than severity of injury in accounting for ODD symptomatology and change in such symptomatology in the first but not the second year after TBI in children and adolescents. This appears related to persistence of new ODD symptomatology after more serious TBI.
We explored relationships between decline in cognitive processing speed (CPS) and change in front... more We explored relationships between decline in cognitive processing speed (CPS) and change in frontal lobe MRI/MRS-based indices of cerebral integrity in 38 healthy adults (age 57-90 years). CPS was assessed using a battery of four timed neuropsychological tests: Grooved Pegboard, Coding, Symbol Digit Modalities Test and Category Fluency (Fruits and Furniture). The neuropsychological tests were factor analyzed to extract two components of CPS: psychomotor (PM) and psychophysical (PP). MRI-based indices of cerebral integrity included three cortical measurements per hemisphere (GM thickness, intergyral and sulcal spans) and two subcortical indices (fractional anisotropy (FA), measured using track-based spatial statistics (TBSS), and the volume of hyperintense WM (HWM)). MRS indices included levels of choline-containing compounds (GPC + PC), phosphocreatine plus creatine (PCr + Cr), and N-acetylaspartate (NAA), measured bilaterally in the frontal WM bundles. A substantial fraction of the variance in the PM-CPS (58%) was attributed to atrophic changes in frontal WM, observed as increases in sulcal span, declines in FA values and reductions in concentrations of NAA and choline-containing compounds. A smaller proportion (20%) of variance in the PP-CPS could be explained by bilateral increases in frontal sulcal span and increases in HWM volumes.
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Papers by Donald Robin