Reaching Toward Visual Targets. I. Neurophysiological Studies

Previous neurophysiological studies have reported that neurons in posterior cingulate cortex (PCC) respond after eye movements, and that these responses may vary with ambient illumination. In monkeys, PCC neurons also respond after the illumination of large visual patterns but not after the illumination of small visual targets on either reflexive saccade tasks or peripheral attention tasks. These observations suggest that neuronal activity in PCC is modulated by behavioral context, which varies with the timing and spatial distribution of visual and oculomotor events. To test this hypothesis, we measured the spatial and temporal response properties of single PCC neurons in monkeys performing saccades in which target location and movement timing varied unpredictably. Specifically, an unsignaled delay between target onset and movement onset permitted us to temporally dissociate changes in PCC activity associated with either event. Response fields constructed from these data demonstrated that many PCC neurons were activated after the illumination of small contralateral visual targets, as well as after the onset of contraversive saccades guided by those targets. In addition, the PCC population maintained selectivity for small contralateral targets during delays of up to 600 ms. Overall, PCC activation was highly variable trial to trial and selective for a broad range of directions and amplitudes. Planar functions described response fields nearly as well as broadly tuned 2-dimensional Gaussian functions. Additionally, the overall responsiveness of PCC neurons decreased during delays when both a fixation stimulus and a saccade target were visible, suggesting a modulation by divided attention. Finally, the strength of the neuronal response after target onset was correlated with saccade accuracy on delayed-saccade trials. Thus PCC neurons may signal salient visual and oculomotor events, consistent with a role in visual orienting and attention.

Download Full-text

A Quick Visual Mind Can be a Slow Auditory Mind

Experimental Psychology (formerly Zeitschrift für Experimentelle Psychologie) ◽

10.1027/1618-3169.56.1.33 ◽

2009 ◽

Vol 56 (1) ◽

pp. 33-40 ◽

Cited By ~ 16

Author(s):

Sander Martens ◽

Addie Johnson ◽

Martje Bolle ◽

Jelmer Borst

Keyword(s):

Attentional Blink ◽

Task Difficulty ◽

Human Mind ◽

Visual Modality ◽

Present Evidence ◽

Conscious Level ◽

Visual Targets ◽

Concurrent Information

The human mind is severely limited in processing concurrent information at a conscious level of awareness. These temporal restrictions are clearly reflected in the attentional blink (AB), a deficit in reporting the second of two targets when it occurs 200–500 ms after the first. However, we recently reported that some individuals do not show a visual AB, and presented psychophysiological evidence that target processing differs between “blinkers” and “nonblinkers”. Here, we present evidence that visual nonblinkers do show an auditory AB, which suggests that a major source of attentional restriction as reflected in the AB is likely to be modality-specific. In Experiment 3, we show that when the difficulty in identifying visual targets is increased, nonblinkers continue to show little or no visual AB, suggesting that the presence of an AB in the auditory but not in the visual modality is not due to a difference in task difficulty.

Download Full-text

More Complicated Mental Tasks Interfere with Drivers' Ability to Detect and Discriminate Among Visual Targets: Spanish Study Tested Actual Highway Drivers; Also Showed Hands-Free Phone Conversations to Be as Safe--or as Risky--as Talking to a Passenger, Depending on the Demands of the Conversation

PsycEXTRA Dataset ◽

10.1037/e307972004-001 ◽

2003 ◽

Author(s):

Keyword(s):

Spanish Study ◽

Visual Targets ◽

Mental Tasks

Download Full-text

Neurophysiological studies of flight-related density-dependent phase characteristics in locusts

Acta Biologica Hungarica ◽

10.1556/abiol.55.2004.1-4.16 ◽

2004 ◽

Vol 55 (1-4) ◽

pp. 137-141 ◽

Cited By ~ 5

Author(s):

A. Ayali ◽

Einat Fuchs ◽

W. Kutsch

Keyword(s):

Density Dependent ◽

Neurophysiological Studies

Download Full-text

Holmes tremor: a delayed complication after resection of brainstem cavernomas

Journal of Neurosurgery ◽

10.3171/2020.7.jns201352 ◽

2020 ◽

pp. 1-11

Author(s):

Marco Cenzato ◽

Davide Colistra ◽

Giorgia Iacopino ◽

Christian Raftopoulos ◽

Ulrich Sure ◽

...

Keyword(s):

Statistical Analysis ◽

Neurophysiological Monitoring ◽

Strict Adherence ◽

Surgical Access ◽

Holmes Tremor ◽

Neurophysiological Studies ◽

Metropolitan Hospital ◽

Delayed Complication ◽

Brainstem Cavernoma ◽

Predicting Factor

OBJECTIVEIn this paper, the authors aimed to illustrate how Holmes tremor (HT) can occur as a delayed complication after brainstem cavernoma resection despite strict adherence to the safe entry zones (SEZs).METHODSAfter operating on 2 patients with brainstem cavernoma at the Great Metropolitan Hospital Niguarda in Milan and noticing a similar pathological pattern postoperatively, the authors asked 10 different neurosurgery centers around the world to identify similar cases, and a total of 20 were gathered from among 1274 cases of brainstem cavernomas. They evaluated the tremor, cavernoma location, surgical approach, and SEZ for every case. For the 2 cases at their center, they also performed electromyographic and accelerometric recordings of the tremor and evaluated the postoperative tractographic representation of the neuronal pathways involved in the tremorigenesis. After gathering data on all 1274 brainstem cavernomas, they performed a statistical analysis to determine if the location of the cavernoma is a potential predicting factor for the onset of HT.RESULTSFrom the analysis of all 20 cases with HT, it emerged that this highly debilitating tremor can occur as a delayed complication in patients whose postoperative clinical course has been excellent and in whom surgical access has strictly adhered to the SEZs. Three of the patients were subsequently effectively treated with deep brain stimulation (DBS), which resulted in complete or almost complete tremor regression. From the statistical analysis of all 1274 brainstem cavernomas, it was determined that a cavernoma location in the midbrain was significantly associated with the onset of HT (p < 0.0005).CONCLUSIONSDespite strict adherence to SEZs, the use of intraoperative neurophysiological monitoring, and the immediate success of a resective surgery, HT, a severe neurological disorder, can occur as a delayed complication after resection of brainstem cavernomas. A cavernoma location in the midbrain is a significant predictive factor for the onset of HT. Further anatomical and neurophysiological studies will be necessary to find clues to prevent this complication.

Download Full-text

NLM-HS: Navigation Learning Model Based on a Hippocampal–Striatal Circuit for Explaining Navigation Mechanisms in Animal Brains

Brain Sciences ◽

10.3390/brainsci11060803 ◽

2021 ◽

Vol 11 (6) ◽

pp. 803

Author(s):

Jie Chai ◽

Xiaogang Ruan ◽

Jing Huang

Keyword(s):

Prefrontal Cortex ◽

Learning Algorithm ◽

Learning Model ◽

Cognitive Map ◽

Model Based ◽

Animal Navigation ◽

Environmental Cognition ◽

Neurophysiological Studies ◽

Planning Algorithm ◽

Two Stages

Neurophysiological studies have shown that the hippocampus, striatum, and prefrontal cortex play different roles in animal navigation, but it is still less clear how these structures work together. In this paper, we establish a navigation learning model based on the hippocampal–striatal circuit (NLM-HS), which provides a possible explanation for the navigation mechanism in the animal brain. The hippocampal model generates a cognitive map of the environment and performs goal-directed navigation by using a place cell sequence planning algorithm. The striatal model performs reward-related habitual navigation by using the classic temporal difference learning algorithm. Since the two models may produce inconsistent behavioral decisions, the prefrontal cortex model chooses the most appropriate strategies by using a strategy arbitration mechanism. The cognitive and learning mechanism of the NLM-HS works in two stages of exploration and navigation. First, the agent uses a hippocampal model to construct the cognitive map of the unknown environment. Then, the agent uses the strategy arbitration mechanism in the prefrontal cortex model to directly decide which strategy to choose. To test the validity of the NLM-HS, the classical Tolman detour experiment was reproduced. The results show that the NLM-HS not only makes agents show environmental cognition and navigation behavior similar to animals, but also makes behavioral decisions faster and achieves better adaptivity than hippocampal or striatal models alone.

Download Full-text

Biomarkers of ketamine’s antidepressant effect: a clinical review of genetics, functional connectivity, and neurophysiology

Chronic Stress ◽

10.1177/24705470211014210 ◽

2021 ◽

Vol 5 ◽

pp. 247054702110142

Author(s):

Alexandra A. Alario ◽

Mark J. Niciu

Keyword(s):

Treatment Response ◽

Antidepressant Treatment ◽

A Priori ◽

Antidepressant Effect ◽

Aspartate Receptor ◽

Neurophysiological Studies ◽

All Cause Mortality ◽

Antidepressant Efficacy ◽

Glutamate Modulators ◽

Response Biomarkers

Major depressive disorder (MDD) is one of the leading causes of morbidity and all-cause mortality (including suicide) worldwide, and, unfortunately, first-line monoaminergic antidepressants and evidence-based psychotherapies are not effective for all patients. Subanesthetic doses of the N-methyl-D-aspartate receptor antagonists and glutamate modulators ketamine and S-ketamine have rapid and robust antidepressant efficacy in such treatment-resistant depressed patients (TRD). Yet, as with all antidepressant treatments including electroconvulsive therapy (ECT), not all TRD patients adequately respond, and we are presently unable to a priori predict who will respond or not respond to ketamine. Therefore, antidepressant treatment response biomarkers to ketamine have been a major focus of research for over a decade. In this article, we review the evidence in support of treatment response biomarkers, with a particular focus on genetics, functional magnetic resonance imaging, and neurophysiological studies, i.e. electroencephalography and magnetoencephalography. The studies outlined here lay the groundwork for replication and dissemination.

Download Full-text