Aperiodic (1/f) neural activity robustly tracks symptom severity changes in treatment-resistant depression.

Background: A reliable physiological biomarker for Major Depressive Disorder is essential for developing and optimizing neuromodulatory treatment paradigms. This study investigates a passive electrophysiologic biomarker that tracks changes in depressive symptom severity on the order of minutes to hours.

Methods: We analyze brief recordings from intracranial electrodes implanted deep in the brain during a clinical trial of deep brain stimulation for treatment-resistant depression in 5 human subjects (n= 3, n = 2).

Interaction of motor behaviour, cortical oscillations and deep brain stimulation in Parkinson disease.

Recent progress in the study of Parkinson's disease (PD) has highlighted the pivotal role of beta oscillations within the basal ganglia-thalamo-cortical network in modulating motor symptoms. Predominantly manifesting as transient bursts, these beta oscillations are central to the pathophysiology of PD motor symptoms, especially bradykinesia. Our central hypothesis is that increased bursting duration in cortex, coupled with kinematics of movement, disrupts the typical flow of neural information, leading to observable changes in motor behavior in PD.

Pilot Study of Acute Behavioral Effects of Pallidal Burst Stimulation in Parkinson's Disease.

Background: Burst-patterned pallidal deep brain stimulation (DBS) in an animal model of Parkinson's disease (PD) yields significantly prolonged therapeutic benefit compared to conventional continuous DBS, but its value in patients remains unclear.

Objectives: The aims were to evaluate the safety and tolerability of acute (<2 hours) burst DBS in PD patients and to evaluate preliminary clinical effectiveness relative to conventional DBS.

Methods: Six PD patients were studied with DBS OFF, conventional DBS, and burst DBS.

Behavior in a visual search task with moving dot stimuli.

Understanding the neuronal mechanisms underlying the processing of visual attention requires a well-designed behavioral task that allows investigators to clearly describe the behavioral effects of attention. Here, we introduce a behavioral paradigm in which one, two or four moving dot stimuli are used in a visual search paradigm that includes two additional attentional conditions. Two animals were trained to make a saccade to a target (a dot patch with net rightward motion) and hold central fixation if no target was present.

Functional neuroanatomy of cognition in Parkinson's disease.

While cognitive dysfunction in Parkinson's disease (PD) is increasingly recognized as a progressive symptom of the underlying neurodegenerative disease, our understanding of the functional and structural anatomic changes underlying these cognitive changes remains incomplete. Like the motor system, research point to a complex interplay between multiple parallel yet interconnected networks or circuits that are affected in PD and give rise to cognitive symptomatology. These circuits are most often studied in the context of disorders of executive function, and tightly linke to frontal lobe dysfunction.

The roles of the lateral intraparietal area and frontal eye field in guiding eye movements in free viewing search behavior.

The lateral intraparietal area (LIP) and frontal eye field (FEF) have been shown to play significant roles in oculomotor control, yet most studies have found that the two areas behave similarly. To identify the unique roles each area plays in guiding eye movements, we recorded 200 LIP neurons and 231 FEF neurons from four animals performing a free viewing visual foraging task. We analyzed how neuronal responses were modulated by stimulus identity and the animals' choice of where to make a saccade.

The functional roles of neural remapping in cortex.

Remapping is a property of some cortical and subcortical neurons that update their responses around the time of an eye movement to account for the shift of stimuli on the retina due to the saccade. Physiologically, remapping is traditionally tested by briefly presenting a single stimulus around the time of the saccade and looking at the onset of the response and the locations in space to which the neuron is responsive. Here we suggest that a better way to understand the functional role of remapping is to look at the time at which the neural signal emerges when saccades are made across a stable scene.

The neural instantiation of a priority map.

The term priority map is commonly used to describe a map of the visual scene, in which objects and locations are represented by their attentional priority, which itself is a combination of low-level salience and top-down control. The aim of this review is to examine how such a map may be represented at the neuronal level. We propose that there is not a single, common map in the brain, but that a number of cortical areas work together to generate the resultant behavior.

Neurons in FEF Keep Track of Items That Have Been Previously Fixated in Free Viewing Visual Search.

When searching a visual scene for a target, we tend not to look at items or locations we have already searched. It is thought that this behavior is driven by an inhibitory tagging mechanism that inhibits responses on priority maps to the relevant items. We hypothesized that this inhibitory tagging signal should be represented as an elevated response in neurons that keep track of stimuli that have been fixated.

Suppression of frontal eye field neuronal responses with maintained fixation.

The decision of where to make an eye movement is thought to be driven primarily by responses to stimuli in neurons' receptive fields (RFs) in oculomotor areas, including the frontal eye field (FEF) of prefrontal cortex. It is also thought that a saccade may be generated when the accumulation of this activity in favor of one location or another reaches a threshold. However, in the reading and scene perception fields, it is well known that the properties of the stimulus at the fovea often affect when the eyes leave that stimulus.

Activity in LIP, But not V4, Matches Performance When Attention is Spread.

The enhancement of neuronal responses in many visual areas while animals perform spatial attention tasks has widely been thought to be the neural correlate of visual attention, but it is unclear whether the presence or absence of this modulation contributes to our striking inability to notice changes in change blindness examples. We asked whether neuronal responses in visual area V4 and the lateral intraparietal area (LIP) in posterior parietal cortex could explain the limited ability of subjects to attend multiple items in a display. We trained animals to perform a change detection task in which they had to compare 2 arrays of stimuli separated briefly in time and found that each animal's performance decreased as function of set-size.

Object comparison in the lateral intraparietal area.

We can search for and locate specific objects in our environment by looking for objects with similar features. Object recognition involves stimulus similarity responses in ventral visual areas and task-related responses in prefrontal cortex. We tested whether neurons in the lateral intraparietal area (LIP) of posterior parietal cortex could form an intermediary representation, collating information from object-specific similarity map representations to allow general decisions about whether a stimulus matches the object being looked for.

LIP activity in the interstimulus interval of a change detection task biases the behavioral response.

When looking around at the world, we can only attend to a limited number of locations. The lateral intraparietal area (LIP) is thought to play a role in guiding both covert attention and eye movements. In this study, we tested the involvement of LIP in both mechanisms with a change detection task.

Remapping, Spatial Stability, and Temporal Continuity: From the Pre-Saccadic to Postsaccadic Representation of Visual Space in LIP.

As our eyes move, we have a strong percept that the world is stable in space and time; however, the signals in cortex coming from the retina change with each eye movement. It is not known how this changing input produces the visual percept we experience, although the predictive remapping of receptive fields has been described as a likely candidate. To explain how remapping accounts for perceptual stability, we examined responses of neurons in the lateral intraparietal area while animals performed a visual foraging task.

Evidence for differential top-down and bottom-up suppression in posterior parietal cortex.

When searching for an object, we usually avoid items that are visually different from the target and objects or places that have been searched already. Previous studies have shown that neural activity in the lateral intraparietal area (LIP) can be used to guide this behaviour; responses to task irrelevant stimuli or to stimuli that have been fixated previously in the trial are reduced compared with responses to potential targets. Here, we test the hypothesis that these reduced responses have a different genesis.

Anticipatory remapping of attentional priority across the entire visual field.

It has been suggested that one way we may create a stable percept of the visual world across multiple eye movements is to pass information from one set of neurons to another around the time of each eye movement. Previous studies have shown that some neurons in the lateral intraparietal area (LIP) exhibit anticipatory remapping: these neurons produce a visual response to a stimulus that will enter their receptive field after a saccade but before it actually does so. LIP responses during fixation are thought to represent attentional priority, behavioral relevance, or value.

Dissociating activity in the lateral intraparietal area from value using a visual foraging task.

We make decisions about where to look approximately three times per second in normal viewing. It has been suggested that eye movements may be guided by activity in the lateral intraparietal area (LIP), which is thought to represent the relative value of objects in space. However, it is not clear how values for saccade goal selection are prioritized while free-viewing in a cluttered visual environment.

Inhibition of return in a visual foraging task in non-human subjects.

Inhibition of return is thought to help guide visual search by inhibiting the orienting of attention to previously attended locations. We have previously shown that, in a foraging visual search task, the neural responses to objects in parietal cortex are reduced after they have been examined. Here we ask whether the animals' reaction times (RTs) in the same task show a psychophysical correlate of inhibition of return: a slowing of reaction time in response to a probe placed at a previously fixated location.

The role of the lateral intraparietal area in orienting attention and its implications for visual search.

Orienting visual attention is of fundamental importance when viewing a visual scene. One of the areas thought to play a role in the guidance of this process is the posterior parietal cortex. In this review, we will describe the way the lateral intraparietal area (LIP) of the posterior parietal cortex acts as a priority map to help guide the allocation of covert attention and eye movements (overt attention).

A pure salience response in posterior parietal cortex.

When exploring a visual scene, some objects perceptually popout because of a difference of color, shape, or size. This bottom-up information is an important part of many models describing the allocation of visual attention. It has been hypothesized that the lateral intraparietal area (LIP) acts as a "priority map," integrating bottom-up and top-down information to guide the allocation of attention.

Microstimulation of posterior parietal cortex biases the selection of eye movement goals during search.

People can find objects in a visual scene fast and effortlessly. It is thought that this may be accomplished by creating a map of the outside world that incorporates bottom-up sensory and top-down cognitive inputs--a priority map. Eye movements are made toward the location represented by the highest activity on the priority map.

Been there, seen that: a neural mechanism for performing efficient visual search.

In everyday life, we efficiently find objects in the world by moving our gaze from one location to another. The efficiency of this process is brought about by ignoring items that are dissimilar to the target and remembering which target-like items have already been examined. We trained two animals on a visual foraging task in which they had to find a reward-loaded target among five task-irrelevant distractors and five potential targets.

State-dependent effects of stimulus presentation duration on the temporal dynamics of neural responses in the inferotemporal cortex of macaque monkeys.

During natural vision, stimuli are viewed for different durations as the state of brain activity changes over time. Here we studied the effects of stimulus presentation duration on cell responses (n=259) in three subdivisions of the inferotemporal (IT) cortex of fixating macaque monkeys as neural baseline firing rates varied over the course of recording. First, cell responses to the presentation of 120 images were tested, and four images that elicited significant responses with various degrees of effectiveness were selected for further study.

Evaluation of relationship between clinical and colonoscopic features in patients with active ulcerative colitis.

Objective: To develop a system to score disease activity based on clinical manifestations in patients with active ulcerative colitis and to assess the relationship of this score with endoscopic disease severity as assessed by colonoscopy.

Methods: In a pilot study of 43 patients, nine clinical variables were examined by univariate analysis. Six factors that correlated with disease severity included age, well-being, defecation frequency, bloody stool, extraintestinal manifestations (Ext) and hemoglobin (Hb).

Object category structure in response patterns of neuronal population in monkey inferior temporal cortex.

Our mental representation of object categories is hierarchically organized, and our rapid and seemingly effortless categorization ability is crucial for our daily behavior. Here, we examine responses of a large number (>600) of neurons in monkey inferior temporal (IT) cortex with a large number (>1,000) of natural and artificial object images. During the recordings, the monkeys performed a passive fixation task.