Modulation of the neuronal response in human primary visual cortex by re-entrant projections during retinal input processing as manifest in the visual evoked potential.

Initial deflections in the visual evoked potential (VEP) reflect the neuronal process of extracting features from the retinal input; a process not modulated by re-entrant projections. Later deflections in the VEP reflect the neuronal process of combining features into an object, a process referred to as 'object closure' and modulated by re-entrant projections. Our earlier work indicated that the VEP reflects independent neuronal responses processing temporal - and spatial luminance contrast and that these responses arise from an interaction between forward and re-entrant input.

How our hearts beat together: a study on physiological synchronization based on a self-paced joint motor task.

Cardiac physiological synchrony is regarded as an important component of social interaction due to its putative role in prosocial behaviour. Yet, the processes underlying physiological synchrony remain unclear. We aim to investigate these processes.

Effects of contact with a dog on prefrontal brain activity: A controlled trial.

Background: There is a broad range of known effects of animal contact on human mental and physical health. Neurological correlates of human interaction with animals have been sparsely investigated. We investigated changes in frontal brain activity in the presence of and during contact with a dog.

Systemic physiology augmented functional near-infrared spectroscopy hyperscanning: a first evaluation investigating entrainment of spontaneous activity of brain and body physiology between subjects.

Functional near-infrared spectroscopy (fNIRS) enables measuring the brain activity of two subjects while they interact, i.e., the hyperscanning approach.

Neural response during temporal - and spatial luminance contrast processing and its manifestation in the blood-oxygen-level-dependent-signal in striate and extra-striate cortex.

The primate visual system has been the prime site for investigating the relationship between stimulus property, neural response and blood-oxygen-level-dependent (BOLD)-signal; yet this relationship remains ill-understood. Electrophysiological studies have shown that the ability to visualise a neural response is determined by stimulus property and presentation paradigm. The neural response in the human visual cortex consists of a phasic response processing temporal and tonic response processing spatial luminance contrast.

Animal presence modulates frontal brain activity of patients in a minimally conscious state: A pilot study.

Integrating animals into therapy is applied increasingly in patients in a minimally conscious state (MCS). This pilot study investigates the effect of animal presence on frontal brain activity in MCS patients compared to healthy subjects. OHB, HHb and tHb of two MCS patients and two healthy adults was measured in frontal cortex using functional near-infrared spectroscopy during three sessions with a live animal and three sessions with a mechanical toy animal present.

An investigation into the relationship between stimulus property, neural response and its manifestation in the visual evoked potential involving retinal resolution.

The visual evoked potential (VEP) has been shown to reflect the size of the neural population activated by a processing mechanism selective to the temporal - and spatial luminance contrast property of a stimulus. We set out to better understand how the factors determining the neural response associated with these mechanisms. To do so we recorded the VEP from 14 healthy volunteers viewing two series of pattern reversing stimuli with identical temporal-and spatial luminance contrast properties.

Shades of grey; Assessing the contribution of the magno- and parvocellular systems to neural processing of the retinal input in the human visual system from the influence of neural population size and its discharge activity on the VEP.

Introduction: Retinal input processing in the human visual system involves a phasic and tonic neural response. We investigated the role of the magno- and parvocellular systems by comparing the influence of the active neural population size and its discharge activity on the amplitude and latency of four VEP components.

Method: We recorded the scalp electric potential of 20 human volunteers viewing a series of dartboard images presented as a pattern reversing and pattern on-/offset stimulus.

Stimuli to differentiate the neural response at successive stages of visual processing using the VEP from human visual cortex.

Background: Clarifying the enigmatic relationship between stimulus property, neural response and the evoked potential is essential if non-invasive functional imaging is to make a meaningful contribution to the understanding of how maturational or degenerative processes influence brain activity. Visual cortex has proven a favourite target to elucidate this relationship. However, to date most studies involving the visual system have yielded inconsistent results or have been strongly criticised.

To see or not to see; the ability of the magno- and parvocellular response to manifest itself in the VEP determines its appearance to a pattern reversing and pattern onset stimulus.

Introduction: The relationship between stimulus property, brain activity, and the VEP is still a matter of uncertainty.

Method: We recorded the VEP of 43 volunteers when viewing a series of dartboard images presented as both a pattern reversing and pattern onset/offset stimulus. Across the dartboard images, the total stimulus area undergoing a luminance contrast change was varied in a graded manner.

Reorganization in Secondary Somatosensory Cortex in Chronic Low Back Pain Patients.

Study Design: A cross-sectional comparative study between chronic low back pain (CLBP) patients and healthy control subjects.

Objective: The aim of this study was to investigate reorganization in the sensory cortex by comparing cortical activity due to mechanosensory stimulation of the lumbar spine in CLBP patients versus a control group by using functional magnetic resonance imaging (fMRI).

Summary Of Background Data: LBP is now the number 1 condition across the world in terms of years living with a disability.

A simple procedure to synchronize concurrent measurements of gait and brain electrical activity and preliminary results from a pilot measurement involving motor-cognitive dual-tasking in healthy older and young volunteers.

Background: The ability to record brain activity under normal walking conditions is the key to studying supraspinal influence on spinal gait control.

New Method: We developed a procedure of synchronizing an electronic walkway (GAITRite, CIR Systems Inc.) with a multi-channel, wireless EEG-system (BrainAmp, Brainproducts).

Determination of thoracic and lumbar spinal processes by their percentage position between C7 and the PSIS level.

Background: Accurate measurements of spinal movement require reliable determination of anatomical landmarks. Current methods of identifying these are not sufficiently reliable or valid for this purpose. A reliable and convenient method of placing markers on selected vertebra is needed to compare measurements between different testers, subjects and sessions.

Visual activation of auditory cortex reflects maladaptive plasticity in cochlear implant users.

Cross-modal reorganization in the auditory cortex has been reported in deaf individuals. However, it is not well understood whether this compensatory reorganization induced by auditory deprivation recedes once the sensation of hearing is partially restored through a cochlear implant. The current study used electroencephalography source localization to examine cross-modal reorganization in the auditory cortex of post-lingually deafened cochlear implant users.

Is adaptive neuronal plasticity an epiphenomenon of the BOLD-signal?

Purpose: This paper will examine different neurocognitive theories which conclude that the brain is able to restore or redress lost or damaged processing systems by reorganising remaining neuronal resources.

Method: The blood oxygenation level dependent or BOLD-signal is the most frequently used method for imaging brain activity in healthy, young adults, children, the elderly, or subjects with a neurodegenerative condition. The BOLD-signal reflects the balance between oxygen metabolism and vascular blood supply.

Maturation of luminance- and motion-defined form perception beyond adolescence: a combined ERP and fMRI study.

Abilities to discriminate forms defined by motion continue to develop throughout childhood. To investigate late development of the visual motion system, we measured brain activity with event-related EEG potentials (ERPs) and functional magnetic resonance imaging (fMRI) in groups of adolescents (15-17 years) and adults (20-30 years) during a visual form discrimination task--with forms being either defined by motion or luminance contrast. We further explored whether possible developmental changes varied with the degree of motion coherence reflecting maturation specific to global motion processing.

NMDA hypofunction in the posterior cingulate as a model for schizophrenia: an exploratory ketamine administration study in fMRI.

Background: Based on animal data, NMDA receptor hypofunction has been suggested as a model for positive symptoms in schizophrenia. NMDA receptor hypofunction affects several corticolimbic brain regions, of which the posterior cingulate seems to be the most sensitive. However, empirical support for a crucial role of posterior cingulate NMDA hypofunction in the pathophysiology of positive symptoms is still missing in humans.

The influence of cortical maturation on the BOLD response: an fMRI study of visual cortex in children.

We performed blood oxygenation level-dependent (BOLD) functional MR imaging in 11 children younger than 5 y of age and 10 children older than 5 y of age. All but five of the children in the older age group were tested under light anesthesia. We examined the cerebral oxidative metabolism (CMRO(2)) associated with the processing of a flashed and a reversing checkerboard stimulus.

An fMRI study of the cerebral macro network involved in 'cue invariant' form perception and how it is influenced by stimulus complexity.

We investigated the influence of stimulus complexity on the macro network of visual areas involved in 'cue invariant' form perception. Functional MRI imaging on 14 healthy, adult volunteers was performed during a two alternative forced choice (2-AFC) form discrimination task. The functional load imposed onto the visual system was varied by using simple and complex shapes.

The BOLD response: a new look at an old riddle.

Functional imaging has struggled for two decades to establish a quantitative link between the neuronal activity and the change in signal obtained. This review proposes a division of neuronal activity into a component relating to the electrical discharge activity and a component relating to the size of the activated neuronal population. These two components are argued to have opposing influences on the BOLD signal.

How much luxury is there in 'luxury perfusion'? An analysis of the BOLD response in the visual areas V1 and V2.

We re-analyzed the functional magnetic resonance imaging data from a study involving awake, adult, human volunteers in order to examine the influence of vascular density on the blood oxygenation level-dependent (BOLD) response. We employed a flashed and reversing stimulus paradigm where the latter stimulated twice the number of receptive fields and with it doubled the neuronal metabolic load (CMRO2) compared to the former stimulus. The blood flow increase to these stimuli was identical, so that differences in the BOLD response are due to differences in the oxygen extraction fraction.

What the little differences between men and women tells us about the BOLD response.

We analyzed the functional MRI signal of 15 men and 15 women. All had been presented with a flashed and a reversing, radial checkerboard stimulus. We investigated both positive and negative blood oxygenation level-dependent (BOLD) responses.

What effect does measuring children under anesthesia have on the blood oxygenation level-dependent signal? A functional magnetic resonance imaging study of visual cortex.

We performed functional magnetic resonance measurements involving visual stimuli on 10 children. Half of the children were measured awake, the other half were measured under light Sevoflurane anesthesia corresponding to 0.5 mean alveolar concentration.

When more means less: a paradox BOLD response in human visual cortex.

The predictions of the 'Linear Transfer Model' (LTM) have been tested only by modulating the frequency of the action potentials while keeping the size of the activated neuronal population constant. The LTM states that the blood oxygenation level-dependent contrast (BOLD) signal is directly proportional to the neuronal activity averaged over milliseconds or seconds. We examined the influence on the BOLD response, of manipulating the size of the activated neuronal population while maintaining the electrical discharge activity constant.

The Effect of Removing Superior Temporal Cortical Motion Areas in the Macaque Monkey: II. Motion Discrimination Using Random Dot Displays.

Nine macaque monkeys were trained to discriminate between a display in which all the dots moved randomly (visual dynamic noise) and an adjacent display in which a proportion of the dots oscillated coherently from side to side. Two monkeys in which area MT (middle temporal visual area) and adjacent regions were surgically removed were unable to perform even the simplest version of this task where the coherent motion was not masked by any visual dynamic noise. The other seven animals tolerated between 60% and 65% of random movement in the otherwise coherently oscillating display before they failed to discriminate between the two displays.