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PubMed2002

Movement-related potentials associated with self-paced, cued and imagined arm movements.

Self-paced movements, movement to a cue and imagined movement have all been reported to be preceded by a prolonged negativity on averaged electroencephalograph (EEG) recordings. Considerable evidence supports an important contribution from the supplementary motor area (SMA) to this potential and all three types of movement have been shown to be associated with SMA activation. This study was designed to compare the premovement component of these movement-related potentials (MRPs) in a group of subjects who performed each of these three types of movement. In addition, in view of the greater SMA activation in association with proximal arm movements, we studied movements at multiple joints in the right arm. All the potentials were largest at Cz. Self-paced movements were preceded by a negativity (mean onset 1.2 s prior to electromyographic activity) with two distinct phases - an early slow increase (early BP, Bereitschaftspotential) and a later, steeper phase (NS', negative slope). Proximal movements were associated with a larger peak amplitude (mean peak amplitude for shoulder 11.6 micro V, finger movement 9.0 micro V at Cz, n=14) due to a bigger NS' phase. Movements to a regular cue, but not to a randomly timed cue, were also preceded by a long duration negativity, but the NS' phase began earlier and was less distinct than for self-paced movements (mean peak amplitude for shoulder movement 9.1 micro V, finger 8.2 micro V at Cz, n=12). Imagining the movements to a regular cue was associated with a slow negativity, with no clear NS' phase (mean peak amplitude for shoulder movement 6.5 micro V, finger 6.2 micro V at Cz). Our results indicate that the MRPs prior to the three types of movement have distinct characteristics, most notably for the NS' phase. The MRP associated with movement to a regular cue may be analogous to the S2-related negativity of the contingent negative variation (CNV). We discuss the findings in the light of current evidence from functional imaging as to the cortical areas activated in similar movements.

Adult↗
PubMed2005

Observation, imagination and execution of an effortful movement: more evidence for a central explanation of motor imagery.

In this study subjects had to imagine, observe and perform a series of 25 squat movements while lifting two dumbbells of 12.5 kg each (one with each hand). This movement is effortful and requires substantial activation of peripheral systems. It was asked whether subjects when they imagined that they were performing the movements or when they observed a model performing the squat movements would show increased activity in EMG, heart rate and respiration compared with a control condition where they sat relaxed in a comfortable chair or a condition where they actually performed the squat movements. Two groups of subjects participated in the experiment: experienced squatters and novices. By employing these two groups we were able to study the differential effect of earlier experience with the target movement on peripheral activation. The results showed that with the exception of respiration no significant peripheral activation could be measured related to motor imagery. Although a clear distinction in experience existed between the experienced squatters versus the novices, no relevant imagery-related differences could be obtained between the two groups. The results are discussed in the light of a central explanation of motor imagery.

Adolescent↗
PubMed2001

Imagined body orientation and perception of the visual vertical.

The existence of body orientation mental imagery was tested by examining whether self roll tilt imagery affects the subjective visual vertical (SVV). Twenty healthy subjects judged the orientation of a dim luminous bar with respect to gravitational vertical, while normally seated in complete darkness with their head firmly restrained earth vertically. SVV was measured in three conditions: a reference condition with no imagery, and a left and a right imagery condition, during which the bar orientation was to be judged while the subjects imagine themselves roll-tilted towards left or right, respectively. The imagined roll tilts were of the same magnitude as roll tilts which generally induce an E-effect, i.e., an SVV lean toward the side opposite to those of body tilt. If imagery and perception of self roll tilt share common processes, self roll tilt imagery should induce an E-like effect. Results show an imagery-induced E-like effect, which strongly supports the idea that humans can perform mental imagery of body orientation about gravity.

Adult↗
PubMed1995

Memory for actual and imagined events in OC checkers.

Information-processing theorists have suggested that obsessive-compulsive (OC) checking may be a function of either (1) an impaired memory of emotional events, (2) an attenuated ability to distinguish between real and imagined events or (3) a dissatisfaction with one's recall without actual memory impairment. These hypotheses were tested by having OC and control Ss engage in real and imagined actions. Some of the actions were designed to produce anxiety in the OC Ss while other events were designed to be emotionally neutral. No differences in reality-monitoring ability were found between OC and control Ss. Contrary to our prediction, OC Ss recall of their last actual behavior was superior to controls, but only for those actions that elicited anxiety. OC Ss, but not controls, reported that they desired higher levels of memory vividness than they were able to produce. The potential mechanism whereby dissatisfaction with memory vividness could contribute to repetitive checking is discussed.

Adult↗
PubMed1990

Cerebral correlates of imagining colours, faces and a map--II. Negative cortical DC potentials.

Cortical activation patterns as measured by negative shifts of the scalp-recorded cortical steady potential ("DC shifts") were assessed in 28 normal subjects during imagining colours, faces, and a spatial map. Imaging resulted in sustained negative DC shifts at temporal, parietal and particularly at occipital sites. The topographic distributions of such DC shifts was modulated as a function of whether spatial or visual imagery was performed. During imaging the spatial map, a parietal maximum was observed, as opposed to a distribution in favour of temporal and occipital sites during imagining faces and colours. Results suggest a neuroanatomical dissociation between visual and spatial imagery. Since a similar visual-spatial dichotomy exists in perception, the finding is interpreted as further evidence of a shared cerebral substrate for images and percepts. The results are discussed in conjunction with the joint blood flow study.

Adult↗
PubMed1995

Effect of imagining and actually tasting a sour taste on one side of the tongue.

To determine whether images can stimulate brainstem reflexes directly, parotid salivation was measured bilaterally in 24 subjects when they imagined, and actually tasted, a sour taste on one side of the tongue. Salivation increased in both cheeks during unilateral gustatory stimulation; furthermore, the response was greater on the stimulated side than contralaterally, indicating that the gustatory reflex has a unilateral component. Subjects imagined the sour taste more clearly after actually experiencing it. However, salivation did not increase significantly during imagery trials, either before or after exposure to the sour taste; in fact, salivation to imagery decreased below baseline after exposure. These findings suggest that extraneous factors (e.g. the emotional connotations of images, anxiety, discomfort, repetitive measurement or fatigue) might sometimes inhibit specific reflex activity induced by images.

Adolescent↗
PubMed1992

Reactivity to alcohol-relevant beverage and imaginal cues in alcoholics.

This study was designed to explore three primary facets of reactivity to alcohol-relevant stimuli among alcoholics: (a) comparison of exposure to an alcohol-containing beverage vs. an appropriate, standardized control beverage; (b) efficacy of imaginally presented cues to elicit reactivity, alone and in combination with beverage cues; and (c) examination of the recovery process. Forty-eight male veterans attending an inpatient alcohol treatment program served as participants and were randomly assigned to one of four groups in a 2 (Alcohol vs. Lemonade Beverage) X 2 (High-Risk vs. Low-Risk Imagery) design. Heart rate reactivity to Beverage cues was consistent with previous research. An interaction of Beverage and Imagery manipulations during recovery revealed both experimental manipulations influenced heart rate, although the Alcohol/High-Risk Imagery exposure group did not demonstrate enhanced effects. Both manipulations also had an impact on ratings of desire to consume alcohol. These findings provide further support for the reliability of cue reactivity effects, and suggest the utility of imaginal exposure procedures as a component of a comprehensive cue reactivity assessment.

Adult↗
PubMed2005

Influence of imagined posture and imagery modality on corticospinal excitability.

Single pulse transcranial magnetic stimulation (TMS) was used to test the assumption that kinesthetic imagery of action is more 'motor' than visual imagery of action. We assessed corticospinal excitability during motor imagery of a thumb-palm opposition movement by recording potentials evoked by TMS from two hand muscles that would (opponens pollicis, OP, target) or would not (abductor digiti minimi, ADM, control) be activated during actual performance of the very same movement. Participants were asked to imagine the thumb-palm opposition movement while maintaining first person imagery that was either purely visual or predominately kinesthetic. The motor imagery task was performed in two conditions in which the imagined and the actual hand could be either congruent or incongruent. Facilitation of potentials recorded from OP was higher during imagery carried out in mentally congruent than incongruent postures. This effect was largely due to lack of excitability recorded during incongruent kinesthetic imagery, which was indistinguishable from baseline imagery of the static hand. All other conditions differed from static imagery regardless of position. No significant effects were found in a control muscle (ADM) thus indicating that the effect was not related to spatial coding. Subjective reports obtained after the experiment indicate that the results cannot be ascribed to qualitative differences in the imagery experienced. For relatively simple motor tasks requiring no 'expertise' we found no detectable difference in the motor cortex due to imagery modality.

Adult↗
PubMed2004

Behavioral and neural correlates of perceived and imagined musical timbre.

The generality of findings implicating secondary auditory areas in auditory imagery was tested by using a timbre imagery task with fMRI. Another aim was to test whether activity in supplementary motor area (SMA) seen in prior studies might have been related to subvocalization. Participants with moderate musical background were scanned while making similarity judgments about the timbre of heard or imagined musical instrument sounds. The critical control condition was a visual imagery task. The pattern of judgments in perceived and imagined conditions was similar, suggesting that perception and imagery access similar cognitive representations of timbre. As expected, judgments of heard timbres, relative to the visual imagery control, activated primary and secondary auditory areas with some right-sided asymmetry. Timbre imagery also activated secondary auditory areas relative to the visual imagery control, although less strongly, in accord with previous data. Significant overlap was observed in these regions between perceptual and imagery conditions. Because the visual control task resulted in deactivation of auditory areas relative to a silent baseline, we interpret the timbre imagery effect as a reversal of that deactivation. Despite the lack of an obvious subvocalization component to timbre imagery, some activity in SMA was observed, suggesting that SMA may have a more general role in imagery beyond any motor component.

Acoustic Stimulation↗
PubMed2000

Evidence of imagined passive self-motion through imagery-perception interaction.

The existence of whole-body passive self-motion mental imagery was investigated by examining whether the perception of passive body accelerations can be affected by passive self-motion imagery. Twenty healthy subjects recognised target passive body acceleration. This recognition task was performed under three conditions: (1) a baseline condition without imagery; (2) a compatible imagery condition during which subjects imagined themselves passively moving in the same direction as the target acceleration; (3) a non-compatible imagery condition during which subjects imagined themselves passively moving in the direction opposite to that of the target acceleration. The recognition of the target acceleration was improved under compatible and degraded under non-compatible imagery. This interaction implies that perception and imaginary share common representations, and supports the existence of passive self-motion imagery.

Acceleration↗
PubMedDate not supplied

Imaginal exposure for anger reduction in adult outpatients: a pilot study.

Although exposure procedures have been widely accepted in the treatment of anxiety disorders, they have rarely been applied to the treatment of anger. The present paper describes an initial attempt to apply an imaginal exposure strategy to adult outpatients (n = 6) referred for anger management. This investigation reflects an empirical clinical practice approach rather than a controlled outcome study. Thus, this paper provides a clinical description of the imaginal exposure program, pre-to-posttest effectiveness data, an exploration of habituation patterns for each participant, and 15-month follow-up data from several patients. In considering the impact of the intervention, statistically significant change was found on most anger variables, the majority of patients met a criteria for clinically significant improvement on important indices of anger, and treatment effect sizes were large and compared favorably to previously studied interventions. Process data revealed a consistent habituation effect, across patients and anger stimuli, in response to repeated exposure practice. Participants' satisfaction was also positive. Finally, statistically significant and clinically meaningful change was evident at 15-months following the intervention. Data from the current pilot project are encouraging and hopefully will stimulate more methodologically rigorous clinical trials.

Adult↗
PubMed1992

The effect of imagery perspectives on the psychophysiological responses to imagined exercise.

The effect of imagery perspectives, i.e. internal imagery vs. external imagery, on the psychophysiological responses to imagined exercise was investigated in the present study. Thirty male and female college students were randomly assigned to perform either internal imagery, external imagery or simple rest in addition to actual exercise. Metabolic, cardiovascular and perceptual responses were recorded before, during and after imagined exercise, actual exercise and rest. The results indicated that internal imagery resulted in a significant increase in ventilation and this response differed from the control condition. Effort sense was higher with internal imagery compared with external imagery. However, both internal and external imagery produced significant elevations in systolic blood pressure (SBP) from pre- to post-imagery, and these values were identical to those observed with actual exercise. Therefore, some responses to imagery were like those seen during actual exercise. Oxygen consumption (VO2), respiratory rate (RR), respiratory exchange ratio (RER), heart rate (HR) and diastolic blood pressure (DBP) were similar between internal and external imagery. It is concluded that the psychophysiological responses to internal imagery resemble actual exercise more than external imagery.

Adolescent↗
PubMed2003

Facilitating perception and imagination in generating change through reflective practice groups.

This paper describes the process of facilitating groups of registered nurses to generate change in themselves and their practice through guided reflection. The concept of perception is explored in respect of individual interpretations of personal experiences where perception becomes reality for that individual. Such perception is subject to bias and without supported guidance in the reflective process inappropriate conclusions are easily generated. Through facilitating group deconstruction of the perceived experience the individual is able to identify the elements of bias emerging and subsequently reaches valid conclusions by reconstructing the experience with reduced elements of subjectivity which are more appropriate to personal and practice development. Within the reconstruction process, imagination is stimulated by steering individuals within the group towards visualising outcomes of planned actions. Use of imagination allows internal acting out of events and the identification of consequences of following a particular course of action. This process enables generation of appropriate actions to take place through development of insight and deeper awareness of influences on personal change. Through appropriate developments in personal approaches the ensuing changes generated in practice take place through considered strategies, which will enhance nursing and care provision.

Attitude of Health Personnel↗
PubMedDate not supplied

Imagined and actual limb selection: a test of preference.

Imagined and actual motor performance were compared to determine what factor(s) drive limb selection for programming movements in contralateral hemispace. Forty right-handed blindfolded subjects were asked to 'reach' via auditory stimulus for a small object placed at multiple locations in hemispace. Two conditions were included: arms uncrossed and arms crossed. With the uncrossed condition, responses were similar. With arms crossed, subjects had the choice of keeping the limbs crossed, reacting to proximity, or uncrossing the arms to reach ipsilaterally. In this condition subjects 'imagined' that they would maintain the crossedposition and reach with the hand closest to the stimulus in both right and left hemispace. However, during 'actual' reaching, responses differed. For left-field stimuli, participants kept the arms crossed, but in response to right-field stimuli, subjects preferred to uncross the limbs in order to reach with the dominant hand. These findings suggest that while motor dominance is the primary factor in limb choice for action in ipsilateral hemispace, it appears that object proximity drives limb selection for reaching in contralateral hemispace.

Adult↗
PubMed2002

The man who executed "imagined" movements: evidence for dissociable components of the body schema.

We examined the nature of representations underlying motor imagery and execution in a patient (CW) with bilateral parietal lesions. When imagining hand movements, CW executed the imagined motor act but was unaware of the movements. These movements were significantly more accurate than volitional movements for the left but not right hand. CW also exhibited preserved motor imagery for the left but not right hand. Consistent with previous accounts, these findings suggest that motor imagery may normally involve the inhibition of movements. CW's unawareness of movements during motor imagery may reflect inattention or misattribution of the unexpected sensory feedback. Furthermore, in line with current models of motor control, motor imagery may depend on the integrity of a "forward model" derived from motor outflow information to generate a prediction of the consequences of a motor command. Such predictions appear to be preserved for imagery of left but not right hand movements in CW. Action may additionally depend on precise updating of effector position derived from the comparison of predicted and actual sensory information. We propose that CW's impaired volitional movements may be attributable to the degradation of such an updating mechanism.

Aged↗
PubMed2000

EEG-based discrimination between imagination of left and right hand movements using Adaptive Gaussian Representation.

This article uses the Adaptive Gaussian Representation (AGR) for human electroencephalogram (EEG) feature extraction aiming the discrimination among mental tasks to be used in a brain computer interface (BCI). It does not focus on the AGR time-frequency representation, but rather on their projection coefficients. Ten volunteers were asked to imagine either right or left hand movement, according to a proper visual stimulus. The features of the resulting EEG signals were characterised by extracting AGR coefficients. Classification was carried out using a Multilayer perceptron (MLP) trained with the classical backpropagation algorithm. Overall results show that AGR coefficients representation is able to reveal a significant EEG discrimination between imagination of right and left hand movement with a mean classification performance of 91%+/-5.8% achieved for female subjects and 87%+/-5.0% achieved for male subjects.

Adult↗
PubMed1998

Ethics and imagination. Implications of cognitive semantics for medical ethics.

Cognitive semantics has made important empirical findings about human conceptualization. In this paper some findings concerning moral concepts are analyzed and their implications for medical ethics discussed. The key idea is that morality has to do with metaphors and imagination rather than with well-defined concepts and deduction. It is argued that normative medical ethics to be psychologically realistic should take these findings seriously. This means that an "imaginative casuistry" is to be preferred compared to principlism and to other forms of casuistry. Furthermore, the metaphorical character of central principles in medical ethics such as autonomy, utility, justice, and integrity is indicated. Such principles are interpreted as rules of thumb summarizing the collective wisdom concerning prototype cases.

Beneficence↗
PubMed1991

Trance logic in hypnosis and imagination.

In 2 experiments we investigated trance logic, or the tolerance of logical incongruity, in age regression and hallucination. Experiment 1 tested 21 hypnotizable and 19 unhypnotizable subjects in an application of the real-simulating model of hypnosis. Experiment 2 tested 26 high and 19 low imagery ability subjects in an adaptation of the model to the imagination context. Subjects' experiences were investigated through the experiential analysis technique. More real than simulating subjects displayed trance logic during age regression, but they did not differ on the major measures of trance logic during hallucination. This pattern of responding occurred in both the hypnosis and the imagination contexts. Subjects' comments suggested that completeness of and belief in age regression or hallucination may play some role in trance logic. The importance of understanding trance logic from the subject's point of view is discussed.

Adolescent↗