Dissociation between dreams and wakefulness: Insights from body and action representations of rare individuals with massive somatosensory deafferentation.

The realism of body and actions in dreams is thought to be induced by simulations based on internal representations used during wakefulness. As somatosensory signals contribute to the updating of body and action representations, these are impaired when somatosensory signals are lacking. Here, we tested the hypothesis that individuals with somatosensory deafferentation have impaired body and actions in their dreams, as in wakefulness.

The role of somatosensation in automatic visuo-motor control: a comparison of congenital and acquired sensory loss.

Studies of chronically deafferented participants have illuminated how regaining some motor control after adult-onset loss of proprioceptive and touch input depends heavily on cognitive control. In this study we contrasted the performance of one such man, IW, with KS, a woman born without any somatosensory fibres. We postulated that her life-long absence of proprioception and touch might have allowed her to automate some simple visually-guided actions, something IW appears unable to achieve.

Perception of body shape and size without touch or proprioception: evidence from individuals with congenital and acquired neuropathy.

The degree to which mental representations of the body can be established and maintained without somatosensory input remains unclear. We contrast two "deafferented" adults, one who acquired large fibre sensory loss as an adult (IW) and another who was born without somatosensation (KS). We compared their responses to those of matched controls in three perceptual tasks: first accuracy of their mental image of their hands (assessed by testing recognition of correct hand length/width ratio in distorted photographs and by locating landmarks on the unseen hand); then accuracy of arm length judgements (assessed by judgement of reaching distance), and finally, we tested for an attentional bias towards peri-personal space (assessed by reaction times to visual target presentation).

Loss of haptic feedback impairs control of hand posture: a study in chronically deafferented individuals when grasping and lifting objects.

Previous work has highlighted the role of haptic feedback for manual dexterity, in particular for the control of precision grip forces between the index finger and thumb. It is unclear how fine motor skills involving more than just two digits might be affected, especially given that loss of sensation from the hand affects many neurological patients, and impacts on everyday actions. To assess the functional consequences of haptic deficits on multi-digit grasp of objects, we studied the ability of three rare individuals with permanent large-fibre sensory loss involving the entire upper limb.

Proprioceptive loss and the perception, control and learning of arm movements in humans: evidence from sensory neuronopathy.

It is uncertain how vision and proprioception contribute to adaptation of voluntary arm movements. In normal participants, adaptation to imposed forces is possible with or without vision, suggesting that proprioception is sufficient; in participants with proprioceptive loss (PL), adaptation is possible with visual feedback, suggesting that proprioception is unnecessary. In experiment 1 adaptation to, and retention of, perturbing forces were evaluated in three chronically deafferented participants.

Mania reduces perceived pain intensity in patients with chronic pain: preliminary evidence from retrospective archival data.

Objective: Bipolar disorder is associated with poor pain outcomes, but the extant literature has not taken into account how mania or hypomania - a central feature of bipolar disorders - influences pain intensity. The objective of this study was to describe whether patients recalled experiencing reduced pain intensity during manic or hypomanic episodes.

Design And Setting: This study used a retrospective design using archival data from patient's medical records.

Generalization of force-field adaptation in proprioceptively-deafferented subjects.

Humans have the remarkable ability to adapt their motor behaviour to changes in body properties and/or environmental conditions, based on sensory feedback such as vision and proprioception. The role of proprioception has been highlighted for the adaptation to new upper-limb dynamics, which is known to generalize to the opposite, non-adapted limb in healthy individuals. Such interlimb transfer seems to depend on sensory feedback, and the present study assessed whether the chronic loss of proprioception precludes interlimb transfer of dynamic adaptation by testing two well-characterized proprioceptively-deafferented subjects.

The fusimotor and reafferent origin of the sense of force and weight.

Signals associated with the command the brain sends to muscles are thought to create the sensation of heaviness when we lift an object. Thus, as a muscle is weakened by fatigue or partial paralysis (neuromuscular blockade), the increase in the motor command needed to lift a weight is thought to explain the increasing subjective heaviness of the lifted object.With different fatiguing contractions we approximately halved the force output of the thumb flexor muscles, which were then used to lift an object.

Exercise slips in high-risk situations and activity patterns in long-term exercisers: an application of the relapse prevention model.

Background: Key factors in successful long-term exercise maintenance are not well understood. The Relapse Prevention Model (RPM) may provide a framework for this process.

Purpose: The purpose of this study was to examine the relationships among characteristics of exercise high-risk situations, components of the RPM relevant to exercise slips, and follow-up exercise outcomes in long-term community exercisers.

Dissociated secondary hyperalgesia in a subject with a large-fibre sensory neuropathy.

In the skin surrounding a site of injury, hyperalgesia develops to mechanical stimuli. Two types of secondary hyperalgesia (to light touch and punctate stimuli) have recently been differentiated, based on different durations and sizes of the area involved. We studied secondary hyperalgesia in a subject who had a loss of myelinated afferent nerve fibres below the neck that spared the A delta group.