Context-dependence of deterministic and nondeterministic contributions to closed-loop steering control.

In natural circumstances, sensory systems operate in a closed loop with motor output, whereby actions shape subsequent sensory experiences. A prime example of this is the sensorimotor processing required to align one's direction of travel, or heading, with one's goal, a behavior we refer to as steering. In steering, motor outputs work to eliminate errors between the direction of heading and the goal, modifying subsequent errors in the process.

New approaches for human epidermal growth factor receptor 2-low and human epidermal growth factor receptor 2-overexpressing metastatic breast cancer.

Purpose Of Review: In recent years, there has been a flurry of activity in the human epidermal growth factor receptor 2 (HER2)-positive metastatic breast cancer space. New, powerful drugs like trastuzumab deruxtecan have challenged our fundamental definition of what HER2 expression means as a predictive biomarker.

Recent Findings: Recent approvals of multiple agents in the second line-metastatic setting have given patients access to a variety of new agents, but also raise questions with regard to optimal sequencing.

Retinal Stabilization Reveals Limited Influence of Extraretinal Signals on Heading Tuning in the Medial Superior Temporal Area.

Heading perception in primates depends heavily on visual optic-flow cues. Yet during self-motion, heading percepts remain stable, even though smooth-pursuit eye movements often distort optic flow. According to theoretical work, self-motion can be represented accurately by compensating for these distortions in two ways: via retinal mechanisms or via extraretinal efference-copy signals, which predict the sensory consequences of movement.

Zebras and Biting Flies: Quantitative Analysis of Reflected Light from Zebra Coats in Their Natural Habitat.

Experimental and comparative evidence suggests that the striped coats of zebras deter biting fly attack, but the mechanisms by which flies fail to target black-and-white mammals are still opaque. Two hypotheses have been proposed: stripes might serve either to defeat polarotaxis or to obscure the form of the animal. To test these hypotheses, we systematically photographed free-living plains zebras in Africa.

Linking sensory neurons to visually guided behavior: relating MST activity to steering in a virtual environment.

Many complex behaviors rely on guidance from sensations. To perform these behaviors, the motor system must decode information relevant to the task from the sensory system. However, identifying the neurons responsible for encoding the appropriate sensory information remains a difficult problem for neurophysiologists.

Mental-health conditions, barriers to care, and productivity loss among officers in an urban police department.

Background: Police officers are frequently exposed to situations that can negatively impact their mental health.

Methods: We conducted this study of an urban police department to determine 1) the prevalence of post-traumatic stress disorder (PTSD), depression, and alcohol abuse; 2) patterns of and barriers to mental-health services utilization; and 3) the impact these conditions have on productivity loss.

Results: Among 150 officers, PTSD (24%), depression (9%), and alcohol abuse (19%) were common.

Parietal area VIP causally influences heading perception during pursuit eye movements.

The ventral intraparietal area (VIP) of the macaque monkey brain is a multimodal area with visual, vestibular, somatosensory, and eye movement-related responses. The visual responses are strongly directional, and VIP neurons respond well to complex optic flow patterns similar to those found during self-motion. To test the hypothesis that visual responses in VIP directly contribute to the perception of self-motion direction, we used electrical microstimulation to perturb activity in VIP while animals performed a two-alternative heading discrimination task.

Monkey steering responses reveal rapid visual-motor feedback.

The neural mechanisms underlying primate locomotion are largely unknown. While behavioral and theoretical work has provided a number of ideas of how navigation is controlled, progress will require direct physiolgical tests of the underlying mechanisms. In turn, this will require development of appropriate animal models.

Extrastriate area MST and parietal area VIP similarly represent forward headings.

Many studies have documented the involvement of medial superior temporal extrastriate area (MST) in the perception of heading based on optic flow information. Furthermore, both heading perception and the responses of MST neurons are relatively stable in the presence of eye movements that distort the retinal flow information on which perception is based. Area VIP in the posterior parietal cortex also contains a robust representation of optic flow cues for heading.

The responses of VIP neurons are sufficiently sensitive to support heading judgments.

The ventral intraparietal area (VIP) of the macaque monkey is thought to be involved in judging heading direction based on optic flow. We recorded neuronal discharges in VIP while monkeys were performing a two-alternative, forced-choice heading discrimination task to relate quantitatively the activity of VIP neurons to monkeys' perceptual choices. Most VIP neurons were responsive to simulated heading stimuli and were tuned such that their responses changed across a range of forward trajectories.

Mechanisms of self-motion perception.

Guiding effective movement through the environment is one of the visual system's most important functions. The pattern of motion that we see allows us to estimate our heading accurately in a variety of environments, despite the added difficulty imposed by our own eye and head movements. The cortical substrates for heading perception include the medial superior temporal area (MST) and the ventral intraparietal area (VIP).

Linear responses to stochastic motion signals in area MST.

The medial superior temporal (MST) area contains neurons with tuning for complex motion patterns, but very little is known about the generation of such responses. To explore how neuronal responses varied across complex motion pattern coherence, we recorded from single units while varying the strength of the global motion pattern in random dot stimuli. Stimuli were a family of optic flow patterns, consisting of radial motion, rotary motion, or combinations thereof ("spiral space").

Clustering of selectivity for optic flow in the ventral intraparietal area.

The presence of a columnar or clustered organization for some property often denotes that this property is important to the local information processing in a cortical area. To determine whether self-motion is systematically organized in the ventral intraparietal area (VIP), we made long electrode penetrations, recording both multi-unit and single-unit tuning for horizontally varying heading stimuli at frequent intervals. Single units were well correlated with the tuning of multi-unit activity at the same location and multi-unit activity was more correlated with tuning at nearby locations than it was with tuning at locations beyond approximately 0.

Parietal area VIP neuronal responses to heading stimuli are encoded in head-centered coordinates.

The ventral intraparietal area (VIP) is a multimodal parietal area, where visual responses are brisk, directional, and typically selective for complex optic flow patterns. VIP thus could provide signals useful for visual estimation of heading (self-motion direction). A central problem in heading estimation is how observers compensate for eye velocity, which distorts the retinal motion cues upon which perception depends.

Optic flow signals in extrastriate area MST: comparison of perceptual and neuronal sensitivity.

The medial superior temporal area of extrastriate cortex (MST) contains signals selective for nonuniform patterns of motion often termed "optic flow." The presence of such tuning, however, does not necessarily imply involvement in perception. To quantify the relationship between these selective neuronal signals and the perception of optic flow, we designed a discrimination task that allowed us to simultaneously record neuronal and behavioral sensitivities to near-threshold optic flow stimuli tailored to MST cells' preferences.

Motion adaptation in area MT.

In many sensory systems, exposure to a prolonged stimulus causes adaptation, which tends to reduce neural responses to subsequent stimuli. Such effects are usually stimulus-specific, making adaptation a powerful probe into information processing. We used dynamic random dot kinematograms to test the magnitude and selectivity of adaptation effects in the middle temporal area (MT) and to compare them to effects on human motion discrimination.

Contrast dependence of response normalization in area MT of the rhesus macaque.

Contrast normalization is a process whereby responses of neurons are scaled according to the total amount of contrast in a region of the image nearby the receptive field of a neuron. This process allows neurons to code for informative scene or object attributes in a manner unaffected by changes in illumination. Evidence for normalization is seen in striate and extrastriate cortex from experiments where multiple stimuli are presented with a single receptive field (RF).

Area MST and heading perception in macaque monkeys.

The macaque medial superior temporal area (MST) is proposed to be specialized for analyzing complex 'optic flow' information. Such space-varying motion patterns provide a rich source of information about self motion, scene structure and object shape. We report the performance of rhesus macaques on a two-alternative 'heading' task, in which they reported whether horizontally varying, simulated trajectories were to left or right of center.

Multiple uses of visual motion. The case for stability in sensory cortex.

The problem of 'readout' from sensory maps has received considerable attention recently. Specifically, many experiments in different systems have suggested that the routing of sensory signals from cortical maps can be impressively flexible. In this review, we discuss many of the experiments addressing readout of motion signals from the middle temporal area (also known as V5) in the macaque monkey.

Extrastriate cortex: A signature of perception grows.

Neuronal activity in area MT of the extrastriate visual cortex is correlated with the choices monkeys make on perceptual tasks. New evidence suggests that this correlation is stronger on some tasks than others.

How are moving images segmented?

Visual images are segmented perceptually by a variety of cues, including color and motion. Recent experiments, using perceptual and neurophysiological approaches, have explored the complex interaction between these attributes. A full account will certainly include the effects of directed attention.

The long-acting beta2-agonist salmeterol xinafoate: effects on airway inflammation in asthma.

Salmeterol xinafoate is an inhaled long-acting beta2-adrenoceptor agonist recently introduced for the treatment of asthma. Both in vitro and animal studies suggest that it may have anti-inflammatory activities of benefit in this disease. To assess this directly, the effects of 6 weeks' treatment with salmeterol on indices of clinical activity, airway dysfunction and inflammation in subjects with stable atopic asthma were investigated.

Spatial summation in the receptive fields of MT neurons.

Receptive fields (RFs) of cells in the middle temporal area (MT or V5) of monkeys will often encompass multiple objects under normal image viewing. We therefore have studied how multiple moving stimuli interact when presented within and near the RF of single MT cells. We used moving Gabor function stimuli, <1 degrees in spatial extent and approximately 100 msec in duration, presented on a grid of possible locations over the RF of the cell.