1: Neuron. 2004 Dec 2;44(5):769-78.

Functional recovery in a primate model of Parkinson's disease following motor
cortex stimulation.

Drouot X, Oshino S, Jarraya B, Besret L, Kishima H, Remy P, Dauguet J,
Lefaucheur JP, Dolle F, Conde F, Bottlaender M, Peschanski M, Keravel Y,
Hantraye P, Palfi S.

URA CEA-CNRS 2210, Service Hospitalier Frederic Joliot, 91401 Orsay, France.

A concept in Parkinson's disease postulates that motor cortex may pattern
abnormal rhythmic activities in the basal ganglia, underlying the genesis of
observed motor symptoms. We conducted a preclinical study of electrical
interference in the primary motor cortex using a chronic MPTP primate model in
which dopamine depletion was progressive and regularly documented using 18F-DOPA
positron tomography. High-frequency motor cortex stimulation significantly
reduced akinesia and bradykinesia. This behavioral benefit was associated with
an increased metabolic activity in the supplementary motor area as assessed with
18-F-deoxyglucose PET, a normalization of mean firing rate in the internal
globus pallidus (GPi) and the subthalamic nucleus (STN), and a reduction of
synchronized oscillatory neuronal activities in these two structures. Motor
cortex stimulation is a simple and safe procedure to modulate
subthalamo-pallido-cortical loop and alleviate parkinsonian symptoms without
requiring deep brain stereotactic surgery.

PMID: 15572109 [PubMed - indexed for MEDLINE]



2: Neuron. 2004 Dec 16;44(6):1057-66.

Frames of reference for eye-head gaze commands in primate supplementary eye
fields.

Martinez-Trujillo JC, Medendorp WP, Wang H, Crawford JD.

Laboratory of Visuomotor Neuroscience, Centre for Vision Research, Canadian
Institutes of Health Research, Group for Action and Perception and Department of
Psychology, CSB York University, Toronto, Ontario M3J 1P3, Canada.
julio.martinez@mcgill.ca

The supplementary eye field (SEF) is a region within medial frontal cortex that
integrates complex visuospatial information and controls eye-head gaze shifts.
Here, we test if the SEF encodes desired gaze directions in a simple retinal
(eye-centered) frame, such as the superior colliculus, or in some other, more
complex frame. We electrically stimulated 55 SEF sites in two head-unrestrained
monkeys to evoke 3D eye-head gaze shifts and then mathematically rotated these
trajectories into various reference frames. Each stimulation site specified a
specific spatial goal when plotted in its intrinsic frame. These intrinsic
frames varied site by site, in a continuum from eye-, to head-, to
space/body-centered coding schemes. This variety of coding schemes provides the
SEF with a unique potential for implementing arbitrary reference frame
transformations.

PMID: 15603747 [PubMed - in process]



3: Neuron. 2004 Dec 16;44(6):925-30.

Modality-specific control of strategic spatial attention in parietal cortex.

Chambers CD, Stokes MG, Mattingley JB.

Cognitive Neuroscience Laboratory, School of Behavioural Science, University of
Melbourne, Victoria 3010, Australia. c.chambers@psych.unimelb.edu.au

The neural basis of selective spatial attention presents a significant challenge
to cognitive neuroscience. Recent neuroimaging studies have suggested that
regions of the parietal and temporal cortex constitute a "supramodal" network
that mediates goal-directed attention in multiple sensory modalities. Here we
used transcranial magnetic stimulation (TMS) to determine which cortical
subregions control strategic attention in vision and touch. Healthy observers
undertook an orienting task in which a central arrow cue predicted the location
of a subsequent visual or somatosensory target. To determine the attentional
role of cortical subregions at different stages of processing, TMS was delivered
to the right hemisphere during cue or target events. Results indicated a
critical role of the inferior parietal cortex in strategic orienting to visual
events, but not to somatosensory events. These findings are inconsistent with
the existence of a supramodal attentional network and instead provide direct
evidence for modality-specific attentional processing in parietal cortex.

PMID: 15603736 [PubMed - in process]



4: Neuron. 2005 Jan 6;45(1):147-56.

Phase Locking of Single Neuron Activity to Theta Oscillations during Working
Memory in Monkey Extrastriate Visual Cortex.

Lee H, Simpson GV, Logothetis NK, Rainer G.

Max Planck Institute for Biological Cybernetics, Spemannstrasse 38, D-72076
Tubingen, Germany.

Working memory has been linked to elevated single neuron discharge in monkeys
and to oscillatory changes in the human EEG, but the relation between these
effects has remained largely unexplored. We addressed this question by measuring
local field potentials and single unit activity simultaneously from multiple
electrodes placed in extrastriate visual cortex while monkeys were performing a
working memory task. We describe a significant enhancement in theta band energy
during the delay period. Theta oscillations had a systematic effect on single
neuron activity, with neurons emitting more action potentials near their
preferred angle of each theta cycle. Sample-selective delay activity was
enhanced if only action potentials emitted near the preferred theta angle were
considered. Our results suggest that extrastriate visual cortex is involved in
short-term maintenance of information and that theta oscillations provide a
mechanism for structuring the recurrent interaction between neurons in different
brain regions that underlie working memory.

PMID: 15629709 [PubMed - in process]



5: Neuron. 2005 Jan 20;45(2):315-323.

Expansion of Direction Space around the Cardinal Axes Revealed by Smooth Pursuit
Eye Movements.

Krukowski AE, Stone LS.

Human Factors Research and Technology Division, NASA Ames Research Center,
Moffett Field, CA 94035 USA.

It is well established that perceptual direction discrimination shows an oblique
effect; thresholds are higher for motion along diagonal directions than for
motion along cardinal directions. Here, we compare simultaneous direction
judgments and pursuit responses for the same motion stimuli and find that both
pursuit and perceptual thresholds show similar anisotropies. The pursuit oblique
effect is robust under a wide range of experimental manipulations, being largely
resistant to changes in trajectory (radial versus tangential motion), speed (10
versus 25 deg/s), directional uncertainty (blocked versus randomly interleaved),
and cognitive state (tracking alone versus concurrent tracking and perceptual
tasks). Our data show that the pursuit oblique effect is caused by an effective
expansion of direction space surrounding the cardinal directions and the
requisite compression of space for other directions. This expansion suggests
that the directions around the cardinal directions are in some way
overrepresented in the visual cortical pathways that drive both smooth pursuit
and perception.

PMID: 15664182 [PubMed - as supplied by publisher]



6: Neuron. 2005 Jan 20;45(2):201-206.

Theta Burst Stimulation of the Human Motor Cortex.

Huang YZ, Edwards MJ, Rounis E, Bhatia KP, Rothwell JC.

Sobell Department of Motor Neuroscience and Movement Disorders, Institute of
Neurology, University College London, Queen Square, London WC1N 3BG, United
Kingdom.

It has been 30 years since the discovery that repeated electrical stimulation of
neural pathways can lead to long-term potentiation in hippocampal slices. With
its relevance to processes such as learning and memory, the technique has
produced a vast literature on mechanisms of synaptic plasticity in animal
models. To date, the most promising method for transferring these methods to
humans is repetitive transcranial magnetic stimulation (rTMS), a noninvasive
method of stimulating neural pathways in the brain of conscious subjects through
the intact scalp. However, effects on synaptic plasticity reported are often
weak, highly variable between individuals, and rarely last longer than 30 min.
Here we describe a very rapid method of conditioning the human motor cortex
using rTMS that produces a controllable, consistent, long-lasting, and powerful
effect on motor cortex physiology and behavior after an application period of
only 20-190 s.

PMID: 15664172 [PubMed - as supplied by publisher]



7: J Neurosci Methods. 2005 Mar 15;142(1):45-54.

Single neuronal recordings using surface micromachined polysilicon
microelectrodes.

Muthuswamy J, Okandan M, Jackson N.

Harrington Department of Bioengineering, ECG 334, College of Engineering and
Applied Science, P.O. Box 879709, Arizona State University, Tempe, AZ
85287-9709, USA.

Bulk micromachining techniques of silicon have been used successfully in the
past several years to microfabricate microelectrodes for monitoring single
neurons in acute and chronic experiments. In this study we report for the first
time a novel surface micromachining technique to microfabricate a very thin
polysilicon microelectrode that can be used for monitoring single-unit activity
in the central nervous system. The microelectrodes are 3mm long and 50mum x
3.75mum in cross-section. Excellent signal to noise ratios in the order of
25-35dB were obtained while recording neuronal action potentials. The
microelectrodes successfully penetrated the brains after a microincision of the
dura mater. Chronic implantation of the microprobe for upto 33 days produced
only minor gliosis. Since the polysilicon shank acts as a conductor, additional
processing steps involved in laying conductor lines on silicon substrates are
avoided. Further, surface micromachining allows for fabricating extremely thin
microelectrodes which could result in decreased inflammatory responses. We
conclude that the polysilicon microelectrode reported here could be a
complementary approach to bulk-micromachined silicon microelectrodes for chronic
monitoring of single neurons in the central nervous system.

PMID: 15652616 [PubMed - in process]



8: Neuron. 2005 Jan 6;45(1):157-67.

The representation of time for motor learning.

Medina JF, Carey MR, Lisberger SG.

Howard Hughes Medical Institute, Department of Physiology and W.M. Keck
Foundation Center for Integrative Neuroscience, University of California, San
Francisco, San Francisco, CA 94143 USA.

We have identified factors that control precise motor timing by studying
learning in smooth pursuit eye movements. Monkeys tracked a target that moved
horizontally for a fixed time interval before changing direction through the
addition of a vertical component of motion. After repeated presentations of the
same target trajectory, infrequent probe trials of purely horizontal target
motion evoked a vertical eye movement around the time when the change in target
direction would have occurred. The pursuit system timed the vertical eye
movement by keeping track of the duration of horizontal target motion and by
measuring the distance the target traveled before changing direction, but not by
learning the position in space where the target changed direction. We conclude
that high temporal precision in motor output relies on multiple signals whose
contributions to timing vary according to task requirements.

PMID: 15629710 [PubMed - in process]