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A long debate in selective attention research is whether attention enhances sensory response or sharpens neural tuning by suppressing response to non-target input. In fact, both processes may occur as a function of load: an uncertain listener might use a broad attentional filter to enhance responses to all inputs (i.e., vigilance), yet employ sharpened tuning to focus on hard to discriminate targets. The present work used the greater signal gain, anatomical precision, and laterality separation of intracranial electrophysiological recordings (electrocorticograms) to investigate these competing effects. Data were recorded from acoustically-responsive cortex in the perisylvian region of a single hemisphere in five neurosurgery patients. Patients performed a dichotic listening task in which they alternately attended toward, away from, or completely ignored (silent reading) tones presented to designated ears at varying presentation rates. Comparisons between the grand-averaged event-related potential (ERP) waveforms show a striking change in the effect of selective auditory attention with attentional load. At slower presentation rates (low-load), ERPs were overall enhanced in response to both input channels and regardless of attended ear, including a significant enhancement of ipsilateral input. This result supports a broadly enhancing model of attention under low perceptual load conditions. At the fastest rate, however, only responses to attended inputs contralateral to grid location remained enhanced. This result supports an increasing suppression, or "sharpening," of neural responses to non-targets with increasing attentional load. These data provide support for an elastic model of attention in which attentional scope narrows with increasing load.

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Deep brain stimulation (DBS) is a common surgical procedure used for the treatment of Parkinson's disease (PD) and essential tremor. A potential complication of this procedure is hardware failure. The authors report a case of DBS hardware failure in which repeated fractures of the extension wire were caused by abnormal rotational movements of the IPG placed in the loose subclavicular tissue of an overweight female. Implantation of the IPG in the suprascapular area prevented further extension wire fractures. This strategy may be especially relevant in overweight females with loose subclavicular tissue.

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UNLABELLED: PET imaging is a powerful tool for measuring physiological changes in the brain during deep brain stimulation (DBS). In this work, we acquired five PET scans using a highly selective D2/D3 dopamine antagonist, 18F-fallypride, to track changes in dopamine receptor availability, as measured by the distribution volume ratio (DVR), through the course of DBS in the bed nucleus of the stria terminalis (BNST) in a nonhuman primate. METHODS: PET scans were performed on a rhesus monkey with unilateral BNST stimulation during periods of baseline, chronic high frequency (130 Hz) and low frequency (50 Hz) DBS stimulation, and during a washout period between stimulation periods. A final scan was performed with the electrode stimulation starting 110 min into the scan. Whole brain parametric images of (18)F-fallypride DVR were calculated for each condition to track changes in both striatal and extrastriatal D2/D3 availability. RESULTS: The monkey displayed significant increases in receptor binding throughout the brain during DBS relative to baseline for 130 and 50 Hz, with changes in DVR of: caudate 42%, 51%; putamen 56%, 57%; thalamus 33%, 49%; substantia nigra 29%, 26%; and prefrontal cortex 28%, 56%, respectively. Washout and post-stimulation scans revealed DVR values close to baseline values. Activating the stimulator midway through the final scan resulted in no statistically significant changes in binding. CONCLUSIONS: PET neuroligand imaging has demonstrated the sensitivity to track changes in dopamine D2/D3 binding during the course of DBS. These methods show great potential for providing insight into the neurochemical consequences of DBS.

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Brain-computer interface (BCI) technology can offer individuals with severe motor disabilities greater independence and a higher quality of life. The BCI systems take recorded brain signals and translate them into real-time actions, for improved communication, movement, or perception. Four patient participants with a clinical need for intracranial electrocorticography (ECoG) participated in this study. The participants were trained over multiple sessions to use motor and/or auditory imagery to modulate their brain signals in order to control the movement of a computer cursor. Participants with electrodes over motor and/or sensory areas were able to achieve cursor control over 2 to 7 days of training. These findings indicate that sensory and other brain areas not previously considered ideal for ECoG-based control can provide additional channels of control that may be useful for a motor BCI.

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OBJECTIVE: Although a relatively new technique, bilateral deep brain stimulation (DBS) of the subthalamic nucleus (STN) for the treatment of advanced cases of Parkinson's disease (PD) shows considerable promise. While the benefits of the STN stimulation for the treatment of motor symptoms of PD are well established, some studies have reported negative neuropsychological outcomes, especially in elderly patients. The objective of the present study was to investigate the neuropsychological effects of bilateral STN-DBS in a small sample of elderly patients with PD. METHODS: Six patients with PD (mean age 73.0 +/- 10.45 years) were assessed both before and approximately 6 months after DBS surgery in six neuropsychological domains. These domains included orientation, estimated IQ, attention/working memory, language, memory, and visual-spatial functioning. Additionally, depressive symptoms were assessed using the Geriatric Depression Scale. Daily doses of antiparkinsonian medications, in levodopa equivalents, were also compared pre- and postoperatively. RESULTS: Antiparkinsonian medications were reduced postoperatively by a mean of 65%, from a mean levodopa equivalent dosage of 987 mg/day to 346 mg/day. Category fluency, a word generation task within the language domain, was the only test in which participants demonstrated a statistically significant decline in performance. Participants demonstrated a mean score decrease of 41% (p < 0.05) in category fluency. CONCLUSIONS: The pathophysiology of the observed deficit remains ill defined. However, despite a small sample size, the study provides further evidence that bilateral STN-DBS in PD patients can be associated with negative neuropsychological outcome in word fluency, especially in elderly patients. Implications regarding patient selection for bilateral STN-DBS and recommendations for future research are further discussed.

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Responses to acoustic input were recorded from human temporal cortex using subdural electrodes in order to investigate in greater anatomical detail how attentional load modulates exogenous auditory responses. Four patient-volunteers performed a dichotic listening task in which they listened for rare frequency deviants in a series of tones presented to both ears at interstimulus intervals (ISIs) of 400, 800, and 2000 ms. Across all ISIs, stimuli presented contralateral to electrode location produced the strongest deflections in the averaged ERP at approximately 90 and 170 ms post-stimulus on average (labeled N90stg and P170stg). Maximal recording sites for these peaks most often occurred over the Sylvian fissure or the upper bank of the posterior superior temporal gyrus. Neither ISI nor selective attention exhibited substantial effects on peak latencies. However, as presentation rates increased (decreasing ISI), overall averaged event-related potential (ERP) amplitudes declined significantly, while attending to the contralateral stimulus significantly increased both the N90stg and P170stg peaks for most patients. This effect of attention increased with decreasing ISI for both components most clearly in the difference between the grand-average ERPs for attending to vs. ignoring the contralateral stimulus, and even more dramatically in the percentage ratio of that difference over the mean peak amplitude. This amplifying effect of attention with increasing load, along with its anatomical location, suggests that attention can enhance exogenous sources in auditory cortex.

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Most current brain-computer interface (BCI) systems for humans use electroencephalographic activity recorded from the scalp, and may be limited in many ways. Electrocorticography (ECoG) is believed to be a minimally-invasive alternative to electroencephalogram (EEG) for BCI systems, yielding superior signal characteristics that could allow rapid user training and faster communication rates. In addition, our preliminary results suggest that brain regions other than the sensorimotor cortex, such as auditory cortex, may be trained to control a BCI system using similar methods as those used to train motor regions of the brain. This could prove to be vital for users who have neurological disease, head trauma, or other conditions precluding the use of sensorimotor cortex for BCI control.

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OBJECTIVE: A central question in auditory electrophysiology has been whether selective attention can modulate exogenous components of the scalp-recorded N1 (the 'N1 effect'). Intracranial electrocorticograms were used in the current work to investigate this issue in greater anatomical detail. METHODS: Data were recorded from subdural electrodes placed across temporal cortex in 6 patient-volunteers undergoing diagnostic procedures for medically intractable epilepsy. Patients performed a dichotic listening task in which they alternately attended to a series of tones presented to both ears (mean ISI 800 ms) by responding to rare frequency deviants. RESULTS: Effects of attention were measured on the largest negative and positive waveform deflections observed between 70 and 220 ms post-stimulus for stimuli presented contralateral to grid location. Peak deflections were most often recorded from the upper bank of the posterior superior temporal gyrus at approximately 89 and 173 ms on average (labeled N90stg and P170stg, respectively). Selective attention had little effect on peak latencies but significantly increased the N90stg for 3 subjects, increased the P170stg for two subjects, and decreased the P170stg for two other subjects. CONCLUSIONS: Selective auditory attention can modulate neural response in auditory cortex. SIGNIFICANCE: The effects of attention on the scalp-recorded N1 component may arise in part from the enhancement of exogenous responses in temporal cortex.

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Functional connections between auditory fields on Heschl's gyrus (HG) and the acoustically responsive posterior lateral superior temporal gyrus (field PLST) were studied using electrical stimulation and recording methods in patients undergoing diagnosis and treatment of intractable epilepsy. Averaged auditory (click-train) evoked potentials were recorded from multicontact subdural recording arrays chronically implanted over the lateral surface of the superior temporal gyrus (STG) and from modified depth electrodes inserted into HG. Biphasic electrical pulses (bipolar, constant current, 0.2 ms) were delivered to HG sites while recording from the electrode array over acoustically responsive STG cortex. Stimulation of sites along the mediolateral extent of HG resulted in complex waveforms distributed over posterolateral STG. These areas overlapped each other and field PLST. For any given HG stimulus site, the morphology of the electrically evoked waveform varied across the STG map. A characteristic waveform was recorded at the site of maximal amplitude of response to stimulation of mesial HG [presumed primary auditory field (AI)]. Latency measurements suggest that the earliest evoked wave resulted from activation of connections within the cortex. Waveforms changed with changes in rate of electrical HG stimulation or with shifts in the HG stimulus site. Data suggest widespread convergence and divergence of input from HG to posterior STG. Evidence is presented for a reciprocal functional projection, from posterolateral STG to HG. Results indicate that in humans there is a processing stream from AI on mesial HG to an associational auditory field (PLST) on the lateral surface of the superior temporal gyrus.

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Chiari malformation is a developmental disorder that is often associated with other abnormalities of the cerebrospinal axis. Despite widespread recognition of this association, there is relatively little information on the treatment of these coexisting disorders in the setting of cerebellar tonsillar ectopia. In an effort to improve the care provided to pediatric patients with Chiari malformations the authors reviewed their management practices over the last 20 years. Specifically, they recorded presenting symptoms, radiological studies, comorbidities, and management (surgical and nonsurgical) of 112 patients (all < 20 years of age) with Chiari malformation without myelodysplasia. They found an associated syrinx in 29% of patients, basilar invagination in 17%, and scoliosis in 14%. The basal angle varied from 120 to 190 degrees and Boogard's angle varied from 120 to 220 degrees ; both angles were larger than those measured in normal controls. The vertical height of the posterior fossa was shortened and the volume decreased as compared with normal controls. The surgical management of this group of patients included posterior decompressive (44%), combined transoral and posterior decompressive (31%), combined posterior decompressive and posterior fusion (8%), and multiple posterior decompressive procedures in the same patient (5%). The authors conclude that pediatric patients with a Chiari malformation should be specifically examined for evidence of additional craniovertebral malformations so that procedures are directed at correcting both the comorbidities and the herniation of the cerebellar tonsils through the foramen.