Linking perceptual learning with identical stimuli to imagery perceptual learning.

Perceptual learning is usually thought to be exclusively driven by the stimuli presented during training (and the underlying synaptic learning rules). In some way, we are slaves of our visual experiences. However, learning can occur even when no stimuli are presented at all. For example, Gabor contrast detection improves when only a blank screen is presented and observers are asked to imagine Gabor patches. Likewise, performance improves when observers are asked to imagine the nonexisting central line of a bisection stimulus to be offset either to the right or left. Hence, performance can improve without stimulus presentation. As shown in the auditory domain, performance can also improve when the very same stimulus is presented in all learning trials and observers were asked to discriminate differences which do not exist (observers were not told about the set up). Classic models of perceptual learning cannot handle these situations since they need proper stimulus presentation, i.e., variance in the stimuli, such as a left versus right offset in the bisection stimulus. Here, we show that perceptual learning with identical stimuli occurs in the visual domain, too. Second, we linked the two paradigms by telling observers that only the very same bisection stimulus was presented in all trials and asked them to imagine the central line to be offset either to the left or right. As in imagery learning, performance improved.

Effects of exposure to food images on physiological reactivity and emotional responses in women with bulimia nervosa / Efecto de la exposición a imágenes de comida sobre la reactividad psicofisiológica y las reacciones emocionales en mujeres con bulimia nerviosa

Background: The aim of this study is to compare the effectiveness of two exposure procedures on habituation of emotional responses to food stimuli: (a) exposure to external cues (food images) without eating forbidden food (CE) and (b) exposure to external cues eating forbidden food (with purge prevention). The influence of craving-trait and mood state on the habituation process is also studied. Method: Emotional modulation of the defense startle reflex was assessed in 26 women at risk of bulimia nervosa. After four exposure trials, changes in the following variables were measured: (a) food craving-state; (b) physiological measures: hearth rate (HR) and skin conductance response (SCR); (c) motivational patterns towards food (defense startle response); and (d) valence, arousal and dominance of the emotional response to food images. Results: After treatment, subjects tended to show non-significant lower SCR and heart orientation responses (vs. defense responses); defense startle response was also significantly lower. Conclusions: The exposure procedure, the induced emotional state and the number of exposure trials are analyzed (AU)

Antecedentes: en este estudio comparamos la eficacia de dos procedimientos de exposición sobre la habituación de reacciones emocionales a alimentos: a) claves externas (imágenes de comida) sin ingerir alimentos prohibidos, y b) claves externas en personas que sí los han ingerido (impidiendo que se produzca el vómito). Además consideramos la influencia de la intensidad del craving rasgo y del estado de ánimo. Evaluamos la modulación emocional del reflejo defensivo de sobresalto motor (RMS) en 26 mujeres con riesgo de padecer bulimia nerviosa. Método: tras cuatro bloques de exposición, se midieron los cambios en: a) craving estado por la comida; b) tasa cardíaca (TC) y respuesta electrodérmica de conductancia (SCR); c) patrones motivacionales ante la comida (RMS); y d) estimaciones afectivas de valencia, arousal y dominancia de las emociones producidas por las imágenes de los alimentos. Resultados: como consecuencia del tratamiento los sujetos tendían a mostrar de forma estadísticamente no significativa menores SCRs y una tendencia de cambio de patrón de respuesta de defensa cardíaca (RD) a respuesta de orientación (RO); sí se apreciaban diferencias significativas en RMS. Conclusiones: se comenta el papel desempeñado por el tipo de exposición utilizado, los estados emocionales inducidos y el número de ensayos de exposición (AU)

Reconocimiento falso y ansiedad estado/rasgo / False recognition and state/trait anxiety

En este estudio se analiza la relación entre la ansiedad estado/rasgo (STAI, State-Trait Anxiety Inventory) y el reconocimiento falso empleando el paradigma Deese/Roediger-McDermott (DRM). En este paradigma, los participantes estudian palabras altamente asociadas a una palabra crítica no presentada; posteriormente, en el test de reconocimiento la palabra crítica se reconoce falsamente. Se presentaron 10 listas de palabras a 161 participantes para estudiar las ilusiones asociativas de memoria. Los resultados mostraron que no existía correlación entre la ansiedad, ni en su modalidad estado ni en su modalidad rasgo, y el reconocimiento falso. Solamente encontramos la esperada correlación positiva entre ansiedad estado y ansiedad rasgo. Posteriormente, los datos obtenidos se analizaron teniendo en cuenta las puntuaciones extremas en ansiedad según el STAI. Así, se comparó el reconocimiento falso de los individuos con alta y baja ansiedad estado, por un lado, y con alta y baja ansiedad rasgo, por otro. De nuevo, los análisis indicaron que no existían diferencia en el nivel de reconocimiento falso ni entre los grupos de alta/baja ansiedad estado ni entre los grupos de alta/baja ansiedad rasgo. En conclusión, estos resultados sugieren que los individuos con alta ansiedad no son más susceptibles a producir ilusiones asociativas de memoria que los individuos con baja ansiedad(AU)

The present study analyzed the relationship between state/trait anxiety and false recognition using the Deese/Roediger-McDermott (DRM) paradigm. In this paradigm, participants study words that are highly associated with a non-presented critical lure; subsequently, when a memory test is administered, the critical lure is consistently recognized falsely. Ten 10-word DRM lists were presented to 161 participants to study associative memory illusions. The results showed no correlation between anxiety (either state or trait assessed using the State-Trait Anxiety Inventory; STAI) and false recognition. Only the expected positive correlation between state anxiety and trait anxiety was found. Thereafter, the results were analyzed according to extreme scores on the STAI. So, high state anxiety individuals were compared with low state anxiety individuals in false recognition, and the same was done with individuals with high versus low trait anxiety. Again, these detailed analyses revealed no differences on the level of false recognition, neither between high/low state anxiety nor between high/low trait anxiety. In conclusion, these findings suggest that individuals with high state anxiety and individuals with high trait anxiety were no more prone to produce associative illusions of memory than individuals with low state and trait anxiet(AU)

Shifting attention within memory representations involves early visual areas.

Prior studies have shown that spatial attention modulates early visual cortex retinotopically, resulting in enhanced processing of external perceptual representations. However, it is not clear whether the same visual areas are modulated when attention is focused on, and shifted within a working memory representation. In the current fMRI study participants were asked to memorize an array containing four stimuli. After a delay, participants were presented with a verbal cue instructing them to actively maintain the location of one of the stimuli in working memory. Additionally, on a number of trials a second verbal cue instructed participants to switch attention to the location of another stimulus within the memorized representation. Results of the study showed that changes in the BOLD pattern closely followed the locus of attention within the working memory representation. A decrease in BOLD-activity (V1-V3) was observed at ROIs coding a memory location when participants switched away from this location, whereas an increase was observed when participants switched towards this location. Continuous increased activity was obtained at the memorized location when participants did not switch. This study shows that shifting attention within memory representations activates the earliest parts of visual cortex (including V1) in a retinotopic fashion. We conclude that even in the absence of visual stimulation, early visual areas support shifting of attention within memorized representations, similar to when attention is shifted in the outside world. The relationship between visual working memory and visual mental imagery is discussed in light of the current findings.

Condicionamiento clásico electrodérmico aversivo y apetitivo utilizando imágenes como estímulos / Aversive and appetitive electrodermal classical conditioning using pictures as stimuli

El principal objetivo de este estudio consistió en comprobar si era posible obtener condicionamiento clásico electrodérmico, tanto aversivo como apetitivo, utilizando imágenes como estímulos condicionados (ECs) y estímulos incondicionados (EIs). Además, se pretendía averiguar si, como consecuencia de dicho condicionamiento, se observaba el fenómeno de disminución de la respuesta incondicionada (RI). Para ello se seleccionaron como estímulos imágenes del IAPS («International Affective Picture System»). Como EI aversivo (EIav) se empleó una fotografía que mostraba un rostro quemado y como EI apetitivo (EIap) una escena de contenido erótico. Tanto el EC aversivo (ECav) como el EC apetitivo (ECap) consistieron en fotografías con valores intermedios de valencia y arousal que mostraban rostros de varones. En el grupo experimental se presentaron 10 ensayos ECav/EIav y otros 10 ensayos ECap/EIap. En el grupo de control cada estímulo (ECav, ECap, EIav y EIap) se presentó en 10 ocasiones en orden pseudoaleatorio. Se registró la respuesta de conductancia electrodérmica (Skin Conductance Response, SCR) elicitada por los ECs y EIs. Los resultados mostraron que se había obtenido condicionamiento aversivo, aunque no apetitivo ni disminución de la RI. Se discuten las dificultades para obtener condicionamiento utilizando imágenes como estímulos y las posibles alternativas para superarlas en futuras investigaciones (AU)

The principal goal of this study was to verify whether it was possible to obtain both aversive and appetitive electrodermal classical conditioning, using pictures as conditioned stimuli (CS), and unconditioned stimuli (US). Additionally, we tried to verify whether, as a consequence of such conditioning, diminution of the unconditioned response (UR) was observed. With this aim, IAPS («International Affective Picture System») pictures were selected as stimuli. A picture showing a burnt face was used as the aversive US (USav), and a picture showing a scene with erotic content was used as the appetitive US (USap). As the aversive CS (CSav), and appetitive CS (CSap), two images with intermediate values of valence and arousal showing male faces were selected. In the experimental group, 10 CSav/USav and 10 CSap/ USap trials were presented. In the control group 10 CSav, CSap, USav, and USap trials were presented in pseudorandom order. Skin conductance response (SCR) elicited by both the CSs and the USs was scored. Results showed aversive conditioning, but neither appetitive conditioning nor UR diminution. Problems to obtain conditioning using pictures as stimuli and possible options to overcome them in future research are discussed (AU)

Time gaps in mental imagery introduced by competing saccadic tasks.

Recently it has been suggested that, somehow similarly to visual saccadic suppression, saccades interrupt some mental activities. After demonstrating that spontaneous eye movements can be used to trace the instantaneous evolution of mental imagery, we show here that making a voluntary saccade or anti-saccade as a secondary task introduces a large delay in a concurrent motion imagery task. An identical task requiring a shift of attention but not saccades also delays imagery, though to a lesser extent. The delay is never compensated afterwards, as if the time dedicated to the secondary task was lost. In contrast, motion imagery is not delayed by spontaneous saccades that accompany imagery, as compared to a fixation condition. We conclude that important time gaps in cognitive activity are introduced only by tasks competing for attentional resources, including voluntary saccades, in dual-task contexts.

Awareness of memory functioning, autobiographical memory and identity in early-stage dementia.

Sense of identity is thought to be closely related to autobiographical memory. Theoretical models of awareness suggest that both may also be related to level of awareness of memory functioning among people with early-stage dementia. This study explores the relationships between autobiographical memory, identity and awareness in early-stage dementia. Thirty participants with Alzheimer's disease, or vascular or mixed dementia were assessed using the Autobiographical Memory Interview, with an additional section eliciting recall for the mid-life period, the Tennessee Self-Concept Scale, and the Memory Awareness Rating Scale. Lower levels of awareness of memory functioning were associated with poorer autobiographical recall for the mid-life period and with a more positive and definite sense of identity. Reduced awareness may serve a protective function against the threats to self posed by the onset and progression of dementia.

Effect of a fatiguing protocol on motor imagery accuracy.

This study was devised to evaluate the influence of muscle fatigue on athletes' ability to perform motor imagery. Performance impairment is a consequence of fatigue, but alterations on perception and mental activity may also occur. To test whether peripheral fatigue affects mental processes, ten sports students imagined three consecutive countermovement jumps before and after a fatiguing protocol, through repetition of upright movements, at 70% of maximal voluntary contraction, until exhaustion. Autonomic nervous system responses and imagined movement durations were considered the dependent variables. Actual duration was systematically overestimated during both visual and kinesthetic imagery, but motor imagery duration and autonomic responses were similar without and under fatigue. Results suggest that muscle fatigue, unlike fatigue induced by prolonged exercise, does not elicit mental fatigue and therefore does not alter motor imagery accuracy.

The binding and recall of snapshot memories in wood ants (Formica rufa L.).

Insects can locate spatial goals by means of 2-D retinotopic views of the surrounding landmarks, which they memorise from the vantage point of the goal. Wood ants acquire such snapshot memories while fixating conspicuous landmarks with frontal retina, and their snapshots extend horizontally at least 120 degrees into the periphery. Are spatially separate items within such an extended snapshot bound together so that a snapshot is recalled as a whole, or are its components recognised individually? We approached this question by training ants to find food midway between two upright black cylinders of different sizes and then examined where they searched when they were given two cylinders of the same size. If the ants know which cylinder replaces the small cylinder and which the large, they should search at a position where the two equal-sized cylinders subtend the same angles as do the training cylinders when viewed from the feeder. Ants conformed to this prediction under one condition, searching at a shorter distance from the substitute for the large cylinder than from the substitute for the small cylinder. But, under another condition, ants were unable to distinguish between the two equal-sized cylinders. Ants failed when white curtains completely surrounded the platform on which the cylinders were placed. They succeeded when one side of the platform had a patterned curtain. We suggest that ants take two snapshots at the feeding site, one when facing the small cylinder and one when facing the large cylinder, and that each snapshot includes the patterned curtain, if it is there. Ants will view the patterned curtain with the lateral retina of one eye when facing the small cylinder and with the lateral retina of the other eye when facing the large cylinder. Our data suggest that there may be associative links between these spatially separate components of the snapshot, which cause the memory of the small cylinder or the large cylinder to be recalled according to which eye sees the curtain. It seems that an extended snapshot not only enhances the accuracy of localisation but can also increase the reliability of snapshot recall, provided that the components of a snapshot are bound together.

Switching skills on by turning off part of the brain.

Snyder and Mitchell (1999) have argued that the extraordinary skills of savants, including mathematics and drawing, are within us all but cannot normally be accessed without some form of brain damage. It has also been argued that such skills can be made accessible to normal people by switching off part of their brain artificially using magnetic pulses (Carter, 1999). Using repetitive transcranial magnetic stimulation (rTMS) to interrupt the function of the frontotemporal lobe, a region of the brain implicated in the development of savant skills (Miller et al., 1996,1998), we tested this hypothesis. Here we show that savant-type skills improved in 5 out of 17 participants during the period of stimulation. The enhanced skills included declarative memory, drawing, mathematics, and calendar calculating. In addition to overall improvement being observed, striking improvements in individual performance on various tasks were also seen.

EEG activity of aviators during imagery flight training.

OBJECTIVE: Imagery flight training (IFT) is widely used in aviation without neurophysiological evaluation. Electroencephalogram (EEG) during IFT was compared between experienced fighter pilots (FP) and novice pilots (NP). METHODS: Six FP and 9 NP performed imagery right bank, left bank, right roll, and left roll maneuvers. Each task was repeated 5 times in a random order. Instantaneous EEG power was calculated by the intertrial variance method. RESULTS: In FP, 3 waves of event-related desynchronization (ERD) were observed. The third ERD (ERD3) was observed at all the electrode positions except Fp1 which began 0.25 s before the beginning of IFT and reached its peak 0.25 s after the beginning of IFT. In NP, ERD was not related to the start of IFT. The difference in event-related EEG at the peak of ERD3 was not significant between FP and NP. However, the negative change to the peak of ERD3 was significantly larger in FP than in NP. CONCLUSIONS: It is speculated that ERD3 in FP may indicate the activation of cortical areas including visual- and motor-related areas involved in IFT. SIGNIFICANCE: It is speculated that the representation of IFT was programmed in visual- and motor-related cortical areas as an aviator's career advances.

Precise oculomotor correlates of visuospatial mental rotation and circular motion imagery.

Visual imagery is a basic form of cognition central to activities such as problem solving or creative thinking. Phenomena such as mental rotation, in which mental images undergo spatial transformations, and motion imagery, in which we imagine objects in motion, are very elusive. For example, although several aspects of visual imagery and mental rotation have been reconstructed through mental chronometry, their instantaneous evolution has never been directly observed. We paired mental chronometry to eye movement recording in subjects performing a visuospatial mental rotation task and an instructed circular motion imagery task. In both tasks, sequences of spontaneous saccades formed curved trajectories with a regular spatio-temporal evolution. In the visuospatial mental rotation task, saccadic amplitude decreased progressively within each sequence, resulting in an average gaze rotation with a bell-shaped asymmetrical angular velocity profile whose peak and mean increased with the amount of the to-be-performed rotation, as in reaching movements. In the second task, the average gaze rotation reproduced faithfully the to-be-imagined constant-velocity circular motion, thus excluding important distortions in the oculomotor performance. These findings show for the first time the instantaneous spatio-temporal evolution of mental rotation and motion imagery. Moreover, the fact that visuospatial mental rotation is modeled as a reaching act suggests that reaching pertains to the realm of visuospatial thinking, rather than being restricted to the motor domain. This approach based on eye movement recording can be profitably coupled to methods such as event-related potentials, transcranial magnetic stimulation, or functional magnetic resonance to study the precise neuronal dynamics associated with an ongoing mental activity.

Misleading postevent information and flashbulb memories.

The aim of this study was to create the conditions of a real discussion concerning the past in an experimental setting and examine their effect on subsequent recollections of important autobiographical events. A total of 55 adults described two episodes twice. The first episode was a typical news reception event and the second one represented a private event of particular personal significance. In between the two recall sessions, participants from the experimental group viewed two films. The first was a short televised account of the two events; the second was a corresponding videotaped description of the personal experiences of a middle-aged man. In addition, participants were asked to imagine what he had been talking about. Most of the participants from the experimental group incorporated elements of the man's description into their own subsequent accounts. In spite of this, they rated the accuracy of their post-test memories as very high. The implications for understanding distortion mechanisms in flashbulb memories are discussed.

Misremembering pictured objects: people of all ages demonstrate the boundary extension illusion.

In the boundary extension illusion, subjects recollect more of a photographed scene than was originally shown. In this study, first- and fifth-grade children, young adult college students, and older adults studied 4 one-object or 4 two-object picture stimuli for 15 s each. Immediately after each visual scene was shown, the subjects drew it from memory inside a rectangle that was the same size as the previous picture. This study demonstrated that all age groups, from young children to older adults, were susceptible to the boundary extension illusion. This finding is discussed in terms of Intraub's perceptual schema hypothesis and Johnson's source-monitoring hypothesis.

Flashbulb memories and other repetitive images: a psychiatric perspective.

The term "flashbulb memory" was used by Brown and Kulik in 1977 to refer to the vivid recollections that humans may have of events considered to be of particular significance to the individual or group. These memories are described as having a photographic quality and as being accompanied by a detail-perfect apparel of contextual information (weather, background music, clothes worn, etc.) pertaining to the time and place where the event was first known. They may even evoke emotions similar to the ones felt upon hearing the news. It has been suggested that flashbulb memories are formed by the activity of an ancient brain mechanism evolved to capture emotional and cognitive information relevant to the survival of the individual or group. Some of the original assumptions made by Brown and Kulik have since been challenged, but the phenomenon in question remains an important area of research. However, the latter is often marred by the fact that flashbulb memories are studied as if they were unique psychological events without parallel in clinical practice. Psychiatrists, however, should consider flashbulb memories as being members of a broad family of experiences that include drug flashbacks, palinopsia, palinacusis, posttraumatic memories, and the vivid and haunting memories experienced by subjects with some forms of mental disorder (e.g., phobias, panic attacks, obsessional disorder, phantom-limb phenomena, and depressive melancholia). All of these experiences share clinical features such as paroxysmal repetition, sensory vividness, a capacity to trigger emotions, dysphoria, and a tendency for the rememberer to shift from the role of actor to that of observer and for the reminiscence to become organized in a stereotyped narrative. Some of these clinical phenomena are discussed, and the suggestion is made that seeking phenomenological and neurobiological common denominators to all of these experiences may be a superior research strategy versus studying flashbulb memories alone.

Cortical blindness and visual imagery.

Controversy exists concerning the neural basis underlying visual imagery. Some propose that visual images evoked from memory are mediated by primary visual cortices. Others argue that these primary visual areas perform computations on elementary visual features when constructing visual representations from retinal input but that they are not activated during recall of these representations. The visual imagery abilities of patients with cortical blindness may resolve this controversy. The proposition that primary visual cortex is necessary for visual imagery predicts a cortically blind subject's inability to perceive visual stimuli would be accompanied by an inability to image visually. Our investigations of three patients with cortical blindness provide strong evidence that primary visual cortices are not essential for the mediation of visual images recalled from memory.

Common mechanisms of visual imagery and perception.

Detection of a visual target can be facilitated by flanking visual masks. A similar enhancement in detection thresholds was obtained when observers imagined the previously perceived masks. Imagery-induced facilitation was detected for as long as 5 minutes after observation of the masks by the targeted eye. These results indicated the existence of a low-level (monocular) memory that stores the sensory trace for several minutes and enables reactivation of early representations by higher processes. This memory, with its iconic nature, may subserve the interface between mental images and percepts.

Use of different imagery perspectives on the learning and performance of different motor skills.

Two experiments are reported which examine the relative efficacy of different imagery perspectives on a slalom type and a gymnastic type task. Twenty-four able-bodies sport, health and physical education students were allocated to either an internal visual imagery group or an external visual imagery group. In both experiments subjects watched video-recordings of someone completing the tasks, then performed five blocks of three trials with feedback after each block, and internal/external visual imagery before each trial. A transfer/retention trial was performed one week later. The tasks were a wheelchair slalom task and a pseudogymnastics routine performed using rhythmic gymnastics clubs to show static positions. The slalom task results suggested that in the retention test, the external visual imagery group focused on the speed of performance, whilst the internal visual imagery group focused on the accuracy of performance. These findings were interpreted as suggesting that internal visual imagery was more effective for the planning of action in response to changes in a visual field. However, in the gymnastics task, contrary to previous suggestions, external visual imagery was found to be more effective than internal visual imagery for both learning and subsequent retention. The roles of internal and external visual imagery are discussed in terms of task characteristics and the observational learning literature.

Interference effects of mental imagery on a motor task.

It can be argued that imaginary practice and physical practice are functionally similar. Evidence in support of this hypothesis comes from several experiments demonstrating that interference effects from imaginary practice in motor learning and motor memory are similar in both direction and size to those resulting from physical practice. The purpose of the present study was to provide additional support for this finding using a retroactive interference paradigm. Sixty participants were required to practise performing a simple motor task that was to be completed in a criterion time of 700 ms. They then were randomly assigned to one of six groups. These groups differed in the amount and type of interpolated practice they experienced. One physical practice group attended one session of interpolated activity involving physical practice of another motor task. The other physical practice group participated in two such sessions. One imagery group attended a single session entailing imaginary practice of the same interpolated motor task, while the other imagery group had two such sessions. A fifth group experienced a combination of physical practice and rest periods for two interpolated sessions. A control group did not experience any interpolated activity sessions. Following the interpolated activity sessions, all groups were given a retention/reacquisition test on the original motor task. Imaginary and physical practice during the interpolated activity sessions caused similar interference effects on retention/reacquisition. All groups showed greater deviation from the criterion movement time (700 ms) during the retention test than the control group, and these deviations were in the expected direction given the nature of the interpolated motor task.

On relations between perceiving, imagining and performing in the learning of cyclical movement sequences.

In three experiments, the effects of observational, mental and physical practice on the performance of cyclical movement sequences were investigated. Experiment 1 revealed that repeated demonstrations of the criterion motion were sufficient for adequate reproductions of the movement form and that mental or physical practice had only small additional effects. Furthermore, consistency of movement tempo and consistency of relative timing, normally seen as dependent on physical practice, were similar in all experimental conditions at the end of practice. Experiment 2 confirmed this counter-intuitive finding by demonstrating equivalent improvements in the consistency of relative timing after physical and mental practice and after practice in a perceptual discrimination task. In Expt 3, discrimination of a nonspatial version of the criterion motion from similar patterns was also found to enhance consistency, indicating that eye movements were not a crucial factor in the observed effects. The findings suggest that performance, observation and imagery of sequential patterns involve a common process, characterized as event generation, which is either coupled to an articulatory system (in the case of physical practice), synchronized with an external event (in the case of observational practice), or 'runs free' without such articulatory or perceptual coupling in the case of imagery.