Motor learning without movement.

Prediction errors guide many forms of learning, providing teaching signals that help us improve our performance. Implicit motor adaptation, for instance, is thought to be driven by sensory prediction errors (SPEs), which occur when the expected and observed consequences of a movement differ. Traditionally, SPE computation is thought to require movement execution. However, recent work suggesting that the brain can generate sensory predictions based on motor imagery or planning alone calls this assumption into question. Here, by measuring implicit motor adaptation during a visuomotor task, we tested whether motor planning and well-timed sensory feedback are sufficient for adaptation. Human participants were cued to reach to a target and were, on a subset of trials, rapidly cued to withhold these movements. Errors displayed both on trials with and without movements induced single-trial adaptation. Learning following trials without movements persisted even when movement trials had never been paired with errors and when the direction of movement and sensory feedback trajectories were decoupled. These observations indicate that the brain can compute errors that drive implicit adaptation without generating overt movements, leading to the adaptation of motor commands that are not overtly produced.

Low-frequency sounds combined with motor imagery elicits a transient disruption of force performance: A path to neuromotor reprogramming?

The effectiveness of motor imagery (MI) training on sports performance is now well-documented. Recently, it has been proposed that a single session of MI combined with low frequency sound (LFS) might enhance muscle activation. However, the neural mechanisms underlying this effect remain unknown. We set up a test-retest intervention over the course of 2 consecutive days to evaluate the effect of (i) MI training (MI, n = 20), (ii) MI combined with LFS (MI + LFS, n = 20), and (iii) a control condition (CTRL, n = 20) on force torque produced across repeated maximal voluntary contractions of the quadriceps before (Pretest), after (Posttest) and at +12 h (Retention) post-intervention. We collected the integrated electromyograms of the quadriceps muscles, as well as brain electrical potentials during each experimental intervention. In the CTRL group, total force torque decreased from Pretest to Retention and from Posttest to Retention. By contrast, there was an increase between Posttest and Retention in both MI + LFS and MI groups (both ηP2 = 0.03, p < 0.05). Regression analyses further revealed a negative relationship between force performance and EEG activity in the MI + LFS group only. The data support a transient interference of LFS on cortical activity underlying the priming effects of MI practice on force performance. Findings are discussed in relation to the potential for motor reprogramming through MI combined with LFS.

Visual Mental Imagery and Neural Dynamics of Sensory Substitution in the Blindfolded Subjects.

Although one can recognize the environment by soundscape substituting vision to auditory signal, whether subjects could perceive the soundscape as visual or visual-like sensation has been questioned. In this study, we investigated hierarchical process to elucidate the recruitment mechanism of visual areas by soundscape stimuli in blindfolded subjects. Twenty-two healthy subjects were repeatedly trained to recognize soundscape stimuli converted by visual shape information of letters. An effective connectivity method called dynamic causal modeling (DCM) was employed to reveal how the brain was hierarchically organized to recognize soundscape stimuli. The visual mental imagery model generated cortical source signals of five regions of interest better than auditory bottom-up, cross-modal perception, and mixed models. Spectral couplings between brain areas in the visual mental imagery model were analyzed. While within-frequency coupling is apparent in bottom-up processing where sensory information is transmitted, cross-frequency coupling is prominent in top-down processing, corresponding to the expectation and interpretation of information. Sensory substitution in the brain of blindfolded subjects derived visual mental imagery by combining bottom-up and top-down processing.

The role of dopamine in visual imagery-An experimental pharmacological study.

Mental imagery enables people to simulate experiences in their minds without the presence of an external stimulus. The underlying biochemical mechanisms are poorly understood but there is vague evidence that dopamine may play a significant role. A better understanding at the biochemical level could help to unravel the mechanisms of mental imagery and related phenomena such as aphantasia (= lack of voluntary mental imagery), but also opens up possibilities for interventions to enhance or restore mental imagery. To test the hypothesis that acute dopamine depletion leads to a decrease in the strength of mental imagery, N = 22 male participants will be administered an amino acid mixture containing branched-chain amino acids (BCAAs) and tryptophan (TRP) to transiently reduce dopamine synthesis and further N = 22 male participants will receive a placebo. Plasma prolactin (PRL) levels are determined as a peripheral marker of brain dopamine function. The strength of mental imagery will be measured before and after ingestion of the BCAA/TRP mixture using the method of mental imagery priming. Additional exploratory analyses will use genetic data to investigate possible effects of variations on dopaminergic gene loci (e.g., DAT1) on dopamine levels and strength of mental imagery. The results show […].

On the relationship between foveal mask interference and mental imagery in peripheral object recognition.

A delayed foveal mask affects perception of peripheral stimuli. The effect is determined by the timing of the mask and by the similarity with the peripheral stimulus. A congruent mask enhances performance, while an incongruent one impairs it. It is hypothesized that foveal masks disrupt a feedback mechanism reaching the foveal cortex. This mechanism could be part of a broader circuit associated with mental imagery, but this hypothesis has not as yet been tested. We investigated the link between mental imagery and foveal feedback. We tested the relationship between performance fluctuations caused by the foveal mask-measured in terms of discriminability (d') and criterion (C)-and the scores from two questionnaires designed to assess mental imagery vividness (VVIQ) and another exploring object imagery, spatial imagery and verbal cognitive styles (OSIVQ). Contrary to our hypotheses, no significant correlations were found between VVIQ and the mask's impact on d' and C. Neither the object nor spatial subscales of OSIVQ correlated with the mask's impact. In conclusion, our findings do not substantiate the existence of a link between foveal feedback and mental imagery. Further investigation is needed to determine whether mask interference might occur with more implicit measures of imagery.

Scene construction in healthy aging - Exploring the interplay between task complexity and oculomotor behaviour.

Mounting evidence indicates a close correspondence between episodic memory, mental imagery, and oculomotor behaviour. It remains unclear, however, how oculomotor variables support endogenously driven forms of mental imagery and how this relationship changes across the adult lifespan. In this study we investigated age-related changes in oculomotor signatures during scene construction and explored how task complexity impacts these processes. Younger and cognitively healthy older participants completed a guided scene construction paradigm where scene complexity was manipulated according to the number of elements to be sequentially integrated. We recorded participants' eye movements and collected subjective ratings regarding their phenomenological experience. Overall, older adults rated their constructions as more vivid and more spatially integrated, while also generating more fixations and saccades relative to the younger group, specifically on control trials. Analyses of participants' total scan paths revealed that, in the early stages of scene construction, oculomotor behaviour changed as a function of task complexity within each group. Following the introduction of a second stimulus, older but not younger adults showed a significant decrease in the production of eye movements. Whether this shift in oculomotor behaviour serves a compensatory function to bolster task performance represents an important question for future research.

The influence of imagery vividness and internally-directed attention on the neural mechanisms underlying the encoding of visual mental images into episodic memory.

Attention can be directed externally toward sensory information or internally toward self-generated information. Using electroencephalography (EEG), we investigated the attentional processes underlying the formation and encoding of self-generated mental images into episodic memory. Participants viewed flickering words referring to common objects and were tasked with forming visual mental images of the objects and rating their vividness. Subsequent memory for the presented object words was assessed using an old-new recognition task. Internally-directed attention during image generation was indexed as a reduction in steady-state visual evoked potentials (SSVEPs), oscillatory EEG responses at the frequency of a flickering stimulus. The results yielded 3 main findings. First, SSVEP power driven by the flickering word stimuli decreased as subjects directed attention internally to form the corresponding mental image. Second, SSVEP power returned to pre-imagery baseline more slowly for low- than high-vividness later remembered items, suggesting that longer internally-directed attention is required to generate subsequently remembered low-vividness images. Finally, the event-related-potential difference due to memory was more sustained for subsequently remembered low- versus high-vividness items, suggesting that additional conceptual processing may have been needed to remember the low-vividness visual images. Taken together, the results clarify the neural mechanisms supporting the encoding of self-generated information.

Neural retrieval processes occur more rapidly for visual mental images that were previously encoded with high-vividness.

Visual mental imagery refers to our ability to experience visual images in the absence of sensory stimulation. Studies have shown that visual mental imagery can improve episodic memory. However, we have limited understanding of the neural mechanisms underlying this improvement. Using electroencephalography, we examined the neural processes associated with the retrieval of previously generated visual mental images, focusing on how the vividness at generation can modulate retrieval processes. Participants viewed word stimuli referring to common objects, forming a visual mental image of each word and rating the vividness of the mental image. This was followed by a surprise old/new recognition task. We compared retrieval performance for items rated as high- versus low-vividness at encoding. High-vividness items were retrieved with faster reaction times and higher confidence ratings in the memory judgment. While controlling for confidence, neural measures indicated that high-vividness items produced an earlier decrease in alpha-band activity at retrieval compared with low-vividness items, suggesting an earlier memory reinstatement. Even when low-vividness items were remembered with high confidence, they were not retrieved as quickly as high-vividness items. These results indicate that when highly vivid mental images are encoded, the speed of their retrieval occurs more rapidly, relative to low-vivid items.

Dual-stream cortical pathways mediate sensory prediction.

Predictions are constantly generated from diverse sources to optimize cognitive functions in the ever-changing environment. However, the neural origin and generation process of top-down induced prediction remain elusive. We hypothesized that motor-based and memory-based predictions are mediated by distinct descending networks from motor and memory systems to the sensory cortices. Using functional magnetic resonance imaging (fMRI) and a dual imagery paradigm, we found that motor and memory upstream systems activated the auditory cortex in a content-specific manner. Moreover, the inferior and posterior parts of the parietal lobe differentially relayed predictive signals in motor-to-sensory and memory-to-sensory networks. Dynamic causal modeling of directed connectivity revealed selective enabling and modulation of connections that mediate top-down sensory prediction and ground the distinctive neurocognitive basis of predictive processing.

Aphantasia and involuntary imagery.

Aphantasia is a condition that is often characterized as the impaired ability to create voluntary mental images. Aphantasia is assumed to selectively affect voluntary imagery mainly because even though aphantasics report being unable to visualize something at will, many report having visual dreams. We argue that this common characterization of aphantasia is incorrect. Studies on aphantasia are often not clear about whether they are assessing voluntary or involuntary imagery, but some studies show that several forms of involuntary imagery are also affected in aphantasia (including imagery in dreams). We also raise problems for two attempts to show that involuntary images are preserved in aphantasia. In addition, we report the results of a study about afterimages in aphantasia, which suggest that these tend to be less intense in aphantasics than in controls. Involuntary imagery is often treated as a unitary kind that is either present or absent in aphantasia. We suggest that this approach is mistaken and that we should look at different types of involuntary imagery case by case. Doing so reveals no evidence of preserved involuntary imagery in aphantasia. We suggest that a broader characterization of aphantasia, as a deficit in forming mental imagery, whether voluntary or not, is more appropriate. Characterizing aphantasia as a volitional deficit is likely to lead researchers to give incorrect explanations for aphantasia, and to look for the wrong mechanisms underlying it.

The role of visual imagery in story reading: Evidence from aphantasia.

Aphantasia is a condition in which people are unable to experience visual imagery. Since visual imagery is thought to be key to language processing, we hypothesized the experience of a story would differ between individuals with aphantasia and controls. Forty-seven individuals with aphantasia were compared to fifty-one matched controls on their experience of reading a short story and their general reading habits. Aphantasics were less likely to be engaged with, interested in, and absorbed in the story, and experienced reduced emotional engagement with and sympathy for the story characters, compared to controls. Yet, aphantasics and controls did not differ in how much they liked or appreciated the story, and in general, the reading habits of the two groups also did not differ. Results have implications for embodied theories of language, suggesting visual imagery may influence how a story is experienced, but it is not the only route to story enjoyment.

Properties of imagined experience across visual, auditory, and other sensory modalities.

Little is known about the perceptual characteristics of mental images nor how they vary across sensory modalities. We conducted an exhaustive survey into how mental images are experienced across modalities, mainly targeting visual and auditory imagery of a single stimulus, the letter "O", to facilitate direct comparisons. We investigated temporal properties of mental images (e.g. onset latency, duration), spatial properties (e.g. apparent location), effort (e.g. ease, spontaneity, control), movement requirements (e.g. eye movements), real-imagined interactions (e.g. inner speech while reading), beliefs about imagery norms and terminologies, as well as respondent confidence. Participants also reported on the five traditional senses and their prominence during thinking, imagining, and dreaming. Overall, visual and auditory experiences dominated mental events, although auditory mental images were superior to visual mental images on almost every metric tested except regarding spatial properties. Our findings suggest that modality-specific differences in mental imagery may parallel those of other sensory neural processes.

Slower but more accurate mental rotation performance in aphantasia linked to differences in cognitive strategies.

Mental rotation tasks are frequently used as standard measures of mental imagery. However, aphantasia research has brought such use into question. Here, we assessed a large group of individuals who lack visual imagery (aphantasia) on two mental rotation tasks: a three-dimensional block-shape, and a human manikin rotation task. In both tasks, those with aphantasia had slower, but more accurate responses than controls. Both groups demonstrated classic linear increases in response time and error-rate as functions of angular disparity. In the three-dimensional block-shape rotation task, a within-group speed-accuracy trade-off was found in controls, whereas faster individuals in the aphantasia group were also more accurate. Control participants generally favoured using object-based mental rotation strategies, whereas those with aphantasia favoured analytic strategies. These results suggest that visual imagery is not crucial for successful performance in classical mental rotation tasks, as alternative strategies can be effectively utilised in the absence of holistic mental representations.

Nature's beauty versus urban bustle: Chinese folk music influences food choices by inducing mental imagery of different scenes.

Previous research has demonstrated that music can impact people's food choices by triggering emotional states. We reported two virtual reality (VR) experiments designed to examine how Chinese folk music influences people's food choices by inducing mental imagery of different scenes. In both experiments, young healthy Chinese participants were asked to select three dishes from an assortment of two meat and two vegetable dishes while listening to Chinese folk music that could elicit mental imagery of nature or urban scenes. The results of Experiment 1 revealed that they chose vegetable-forward meals more frequently while listening to Chinese folk music eliciting mental imagery of nature versus urban scenes. In Experiment 2, the participants were randomly divided into three groups, in which the prevalence of their mental imagery was enhanced, moderately suppressed, or strongly suppressed by performing different tasks while listening to the music pieces. We replicated the results of Experiment 1 when the participants' mental imagery was enhanced, whereas no such effect was observed when the participants' mental imagery was moderately or strongly suppressed. Collectively, these findings suggest that music may influence the food choices people make in virtual food choice tasks by inducing mental imagery, which provides insights into utilizing environmental cues to promote healthier food choices.

Does context matter for memory? Testing the effectiveness of learning by imagining situated interactions with objects.

Mounting evidence supports the efficacy of mental imagery for verbal information retention. Motor imagery, imagining oneself interacting physically with the object to be learned, emerges as an optimal form compared to less physically engaging imagery. Yet, when engaging in mental imagery, it occurs within a specific context that may affect imagined actions and consequently impact the mnemonic benefits of mental imagery. In a first study, participants were given instructions for incidental learning: mental rehearsal, visual imagery, motor imagery or situated motor imagery. The latter, which involved imagining physical interaction with an item within a coherent situation, produced the highest proportion of correct recalls. This highlights memory's role in supporting situated actions and offers the possibility for further developing the mnemonic potential of embodied mental imagery. Furthermore, item-level analysis showed that individuals who engaged in situated motor imagery remembered words primarily due to the sensorimotor characteristics of the words' referent. A second study investigating the role of inter-item distinctiveness in this effect failed to determine the extent to which the situational and motor elements need to be distinctive in order to be considered useful retrieval cues and produce an optimal memory performance.

Does Prospective Mental Imagery Predict Symptoms of Negative Affect and Anhedonia in Young People?

Adolescent depression is associated with unhelpful emotional mental imagery. Here, we investigated whether vividness of negative and positive prospective mental imagery predict negative affect and anhedonia in adolescents. 111 people from Israel completed measures of prospective mental imagery, negative affect, and anhedonia at two time-points approximately three months apart. Using three cross-lagged panel models, we showed once 'concurrent' (across-variable, within-time) and 'stability' paths (across-time, within-variable) were estimated, there were no significant cross-lag paths between: i) T1 prospective negative mental imagery and T8 negative affect (i.e. increased vividness of negative future imagery at Time 1 did not predict increased negative affect at Time 8); ii) T1 prospective positive mental imagery and T8 negative affect (i.e. reduced vividness of positive future imagery at Time 1 did not predict increased negative affect at Time 8); and iii) T1 prospective positive mental imagery and T8 anhedonia (i.e. reduced vividness of positive future imagery at Time 1 did not predict increased anhedonia at Time 8). Given high levels of attrition, future research should aim to explore these associations in a larger, more diverse population, as such data could inform on whether modifying earlier prospective mental imagery may influence later time/context-specific effects of prospective mental imagery on negative affect and anhedonia.

Marian apparitions: A multidisciplinary approach. The case of Île Bouchard.

Discussing Marian apparitions in the light of current knowledge in neuroscience is a challenge: the testimonies are often old and indirect, and the "visionaries" could not be questioned or even examined according to current neurological or psychiatric standards. In doing so, we are not unaware of the heterogeneity of seers and the facts they reported: there is not necessarily a single hypothesis. It is the appearances of Île Bouchard that will be discussed here. Our interpretation calls on two non-exclusive "mechanisms": on the one hand, mental imagery, which we know can be unconscious and is modulated or generated by frontal "top-down" mechanisms; on the other hand, the sociological consideration of events, using the concept of enchantment.

Exploring Temporal Relationships Between Anxiety, Mood and Mental Imagery in Patients With Bipolar Disorder: A Network Analysis.

INTRODUCTION: Bipolar disorder is a severe mental health problem with limited treatment success. There is a call for improving interventions, requiring an increased understanding of factors driving mood instability. One promising avenue is to study temporal associations between factors that appear relevant according to the emotional amplifier model of Holmes are changes in mood, anxiety and mental imagery. METHODS: The current study used data from a recent RCT for a secondary analysis which applied a network analysis approach to explore temporal associations between weekly measurements of mania, depression, anxiety and mental imagery measured during 32 weeks in two randomised groups (N = 55) receiving either imagery-focused cognitive therapy (ImCT) or group psychoeducation (PE). RESULTS: Both negative intrusive mental imagery and anxiety appeared central in the network analyses, driving changes in both mania and depression, but only in the PE group. In the ImCT group, only anxiety was driving changes in mania and depression. CONCLUSION: Although exploratory, findings suggest that prior increases in anxiety and negative intrusive mental imagery might be associated with subsequent increases in depression and mania symptoms in patients with bipolar disorder. Anxiety might in turn increase negative intrusive imagery and associated negative emotions. Although more research is needed, results are in line with the emotional amplifier model and stress that future interventions with a focus on anxiety and imagery might help to improve psychosocial therapies for patients with bipolar disorder. In addition, this study suggests that a network approach is a helpful and feasible way to study mood instability, anxiety and mental imagery to increase our understanding of mechanisms underpinning mood instability.

The Impact of Mental Imagery Instructions on Patients' and Therapists' Positive Affect and Strength-Based Behaviours Within Psychotherapy Sessions: A Randomized Controlled Process Study.

OBJECTIVE: Increased attention has recently been paid to the well-being and flourishing of patients in psychotherapy. This study investigated the occurrence of positive affect (PA) and strength-based behaviours within psychotherapy sessions contrasting positive versus neutral imagery instructions. METHODS: This is a secondary analysis of a randomized controlled trial. Seventy-eight sessions of cognitive behavioural therapy involving 26 patients (69.23% female; Mage = 40.31) treated by 13 therapists were selected. PA and strength-based behaviours of patients and therapists were coded on a minute-by-minute basis with the Resource-Oriented Microprocess Analysis. Each session started with a brief mental imagery instruction. Data were analysed using multilevel modelling. RESULTS: Mild levels of PA were very common, whereas stronger expressions were occasional, especially at the beginning and end of sessions. Strength-based behaviours were employed in one-fifth of the videos analysed. Therapists in the positive imagery instruction showed more strength-based behaviours in the beginning phase of sessions, p < 0.05. The two imagery instructions significantly differed in the session trajectories of PA, p < 0.05. A quadratic trend with higher initial values and a sharper decline in PA were found in the positive instruction, whereas the neutral instruction showed a flatter trend. CONCLUSION: Patients and therapists experience PA and discuss strengths in psychotherapy sessions despite patients' distress. The positive imagery instructions potentially induced a positive focus at baseline for therapists but had a negligible effect on the subsequent session progression. TRIAL REGISTRATION: ClinicalTrials.gov identifier: NCT03767101 (registered December 6, 2018).

Imagery-Focused Therapy for Visual Hallucinations: A Case Series.

INTRODUCTION: Visual hallucinations (VH) are more common than previously thought and are linked to higher levels of distress and disability in people with a psychotic illness. Despite this, scant attention has been given to VHs in the clinical literature, and the few therapy case series of cognitive behavioural therapy (CBT) published to date have not demonstrated reliable change. In other areas of clinical research, problematic mental imagery has been found to be more strongly related to negative affect in psychological disorders than negative linguistic thinking, and imagery focused techniques have commonly been found to improve the outcomes in CBT trials. Given VHs have many similarities with visual mental imagery and many of the distressing beliefs associated with VHs targeted in CBT are maintained by accompanying mental imagery (i.e., imaging a hallucinated figure attacking them), it seems plausible that an imagery-focused approach to treating VHs may be most effective. METHODS: The current study is a multiple baseline case series (N = 11) of a 10-session imagery-focused therapy for VH in a transdiagnostic sample. RESULTS: The study had good attendance and feedback, no adverse events and only one [seemly unrelated] drop-out, suggesting good feasibility, safety and acceptability. The majority of clients reported reduction on both full-scale measures (administered at 3 baselines, midtherapy, posttherapy and 3-month follow-up) and weekly measures of VH severity and distress, ranging from medium to large effect sizes. CONCLUSIONS: The case series suggests that an imagery-focused approach to treating VHs may be beneficial, with a recommendation for more rigorous clinical trials to follow.