Pseudorandom Order Research Articles

Caching for where and what: evidence for a mnemonic strategy in a scatter-hoarder.

Scatter-hoarding animals face the task of maximizing retrieval of their scattered food caches while minimizing loss to pilferers. This demand should select for mnemonics, such as chunking, i.e. a hierarchical cognitive representation that is known to improve recall. Spatial chunking, where caches with the same type of content are related to each other in physical location and memory, would be one such mechanism. Here we tested the hypothesis that scatter-hoarding eastern fox squirrels (Sciurus niger) are organizing their caches in spatial patterns consistent with a chunking strategy. We presented 45 individual wild fox squirrels with a series of 16 nuts of four different species, either in runs of four of the same species or 16 nuts offered in a pseudorandom order. Squirrels either collected each nut from a different location or collected all nuts from a single location; we then mapped their subsequent cache distributions using GPS. The chunking hypothesis predicted that squirrels would spatially organize caches by nut species, regardless of presentation order. Our results instead demonstrated that squirrels spatially chunked their caches by nut species but only when caching food that was foraged from a single location. This first demonstration of spatial chunking in a scatter hoarder underscores the cognitive demand of scatter hoarding.

Adaptation effects in grasping the Müller-Lyer illusion

Recent results have shown that effects of pictorial illusions in grasping may decrease over the course of an experiment. This can be explained as an effect of sensorimotor learning if we consider a pictorial size illusion as simply a perturbation of visually perceived size. However, some studies have reported very constant illusion effects over trials. In the present paper, we apply an error-correction model of adaptation to experimental data of N=40 participants grasping the Müller-Lyer illusion. Specifically, participants grasped targets embedded in incremental and decremental Müller-Lyer illusion displays in (1) the same block in pseudo-randomised order, and (2) separate blocks of only one type of illusion each. Consistent with predictions of our model, we found an effect of interference between the two types when they were presented intermixed, explaining why adaptation rates may vary depending on the experimental design. We also systematically varied the number of object sizes per block, which turned out to have no effect on the rate of adaptation. This was also in accordance with our model. We discuss implications for the illusion literature, and lay out how error-correction models can explain perception-action dissociations in some, but not all grasping-of-illusion paradigms in a parsimonious and plausible way, without assuming different illusion effects.

EEG and Eye Tracking Signatures of Target Encoding during Structured Visual Search.

EEG and eye tracking variables are potential sources of information about the underlying processes of target detection and storage during visual search. Fixation duration, pupil size and event related potentials (ERPs) locked to the onset of fixation or saccade (saccade-related potentials, SRPs) have been reported to differ dependent on whether a target or a non-target is currently fixated. Here we focus on the question of whether these variables also differ between targets that are subsequently reported (hits) and targets that are not (misses). Observers were asked to scan 15 locations that were consecutively highlighted for 1 s in pseudo-random order. Highlighted locations displayed either a target or a non-target stimulus with two, three or four targets per trial. After scanning, participants indicated which locations had displayed a target. To induce memory encoding failures, participants concurrently performed an aurally presented math task (high load condition). In a low load condition, participants ignored the math task. As expected, more targets were missed in the high compared with the low load condition. For both conditions, eye tracking features distinguished better between hits and misses than between targets and non-targets (with larger pupil size and shorter fixations for missed compared with correctly encoded targets). In contrast, SRP features distinguished better between targets and non-targets than between hits and misses (with average SRPs showing larger P300 waveforms for targets than for non-targets). Single trial classification results were consistent with these averages. This work suggests complementary contributions of eye and EEG measures in potential applications to support search and detect tasks. SRPs may be useful to monitor what objects are relevant to an observer, and eye variables may indicate whether the observer should be reminded of them later.

Electroencephalographic sensorimotor rhythms are modulated in the acute phase following focal vibration in healthy subjects

Few minutes of focal vibration (FV) on limb muscles can improve motor control in neurological (stroke, Parkinson) patients for unknown underlying neurophysiological mechanisms. Here we hypothesized that in healthy volunteers this FV would increase excitability in the primary sensorimotor cortex (S1-M1) during an isometric contraction of the stimulated muscle. The design included an initial control condition with no FV stimulation (Baseline) as well as three short experimental sessions of FV and a Sham (fake) session in a pseudo-random order. In the Baseline condition and immediately after those sessions, electroencephalographic (EEG) activity was recorded during a mild isometric muscle contraction of the right arm. Alpha and beta motor-related EEG power desynchronization (MRPD) at C4 and C3 electrodes overlying Rolandic regions were used as an index of the cortical excitation in S1-M1. Results showed that, compared to the Baseline (no FV) or Sham stimulation, the first two FV sessions showed a cumulative increase in alpha (but not beta) MRPD at C3 electrode, suggesting a specific effect of vibration on the excitability of contralateral S1-M1 generating EEG “mu” rhythms. FV over limb muscles modulates neurophysiological oscillations enhancing excitability of contralateral S1-M1 in healthy volunteers. The proposed mechanism may explain the clinical effects of vibratory rehabilitation in neurological patients with motor deficits.

Regional Brain Responses Are Biased Toward Infant Facial Expressions Compared to Adult Facial Expressions in Nulliparous Women.

Recent neuroimaging studies suggest that neutral infant faces compared to neutral adult faces elicit greater activity in brain areas associated with face processing, attention, empathic response, reward, and movement. However, whether infant facial expressions evoke larger brain responses than adult facial expressions remains unclear. Here, we performed event-related functional magnetic resonance imaging in nulliparous women while they were presented with images of matched unfamiliar infant and adult facial expressions (happy, neutral, and uncomfortable/sad) in a pseudo-randomized order. We found that the bilateral fusiform and right lingual gyrus were overall more activated during the presentation of infant facial expressions compared to adult facial expressions. Uncomfortable infant faces compared to sad adult faces evoked greater activation in the bilateral fusiform gyrus, precentral gyrus, postcentral gyrus, posterior cingulate cortex-thalamus, and precuneus. Neutral infant faces activated larger brain responses in the left fusiform gyrus compared to neutral adult faces. Happy infant faces compared to happy adult faces elicited larger responses in areas of the brain associated with emotion and reward processing using a more liberal threshold of p < 0.005 uncorrected. Furthermore, the level of the test subjects’ Interest-In-Infants was positively associated with the intensity of right fusiform gyrus response to infant faces and uncomfortable infant faces compared to sad adult faces. In addition, the Perspective Taking subscale score on the Interpersonal Reactivity Index-Chinese was significantly correlated with precuneus activity during uncomfortable infant faces compared to sad adult faces. Our findings suggest that regional brain areas may bias cognitive and emotional responses to infant facial expressions compared to adult facial expressions among nulliparous women, and this bias may be modulated by individual differences in Interest-In-Infants and perspective taking ability.

Decoding Target Distance and Saccade Amplitude from Population Activity in the Macaque Lateral Intraparietal Area (LIP).

Primates perform saccadic eye movements in order to bring the image of an interesting target onto the fovea. Compared to stationary targets, saccades toward moving targets are computationally more demanding since the oculomotor system must use speed and direction information about the target as well as knowledge about its own processing latency to program an adequate, predictive saccade vector. In monkeys, different brain regions have been implicated in the control of voluntary saccades, among them the lateral intraparietal area (LIP). Here we asked, if activity in area LIP reflects the distance between fovea and saccade target, or the amplitude of an upcoming saccade, or both. We recorded single unit activity in area LIP of two macaque monkeys. First, we determined for each neuron its preferred saccade direction. Then, monkeys performed visually guided saccades along the preferred direction toward either stationary or moving targets in pseudo-randomized order. LIP population activity allowed to decode both, the distance between fovea and saccade target as well as the size of an upcoming saccade. Previous work has shown comparable results for saccade direction (Graf and Andersen, 2014a,b). Hence, LIP population activity allows to predict any two-dimensional saccade vector. Functional equivalents of macaque area LIP have been identified in humans. Accordingly, our results provide further support for the concept of activity from area LIP as neural basis for the control of an oculomotor brain-machine interface.

Effects of freezing of gait on postural motor learning in people with Parkinson’s disease

Protective postural responses, including stepping, to recover equilibrium are critical for fall prevention and are impaired in people with Parkinson’s disease (PD) with freezing of gait (FoG). Improving protective postural responses through training may reduce falls in this population. However, motor learning, the basis of neurorehabilitation, is also impaired in people with PD and, in particular, people with PD who experience freezing. It is unknown whether people with PD who freeze can improve protective postural responses, and whether these improvements are similar to nonfreezers. Our goal was to assess whether people with freezing can improve protective postural responses and retain these improvements similarly to nonfreezers. Twenty-eight people with PD (13 freezers, 15 nonfreezers) were enrolled. Improvement in protective postural responses was assessed over the course of 25 forward and 25 backward support surface translations (delivered in pseudo-random order). Postural responses were re-assessed 24h later to determine whether improvements were retained. People who freeze did not improve or retain improvement in protective postural responses as well as nonfreezers in our primary outcome variable, center of mass (COM) displacement after perturbations (post hoc across group assessments: freezers- p=0.14 and nonfreezers- p=0.001, respectively). However, other protective stepping outcomes, including margin of stability, step length, and step time, improved similarly across groups. Significant improvements were retained in both groups. In conclusion, people with PD who freeze exhibited reduced ability to improve protective postural responses in some, but not all, outcome variables. Additional training may be necessary to improve protective postural responses in people with PD who freeze.

Responsiveness of electrical nociceptive detection thresholds to capsaicin (8%)-induced changes in nociceptive processing.

Pain disorders can be initiated and maintained by malfunctioning of one or several mechanisms underlying the nociceptive function. Psychophysical procedures allow the estimation of nociceptive detection thresholds using intra-epidermal electrical stimuli. By varying the temporal properties of electrical stimuli, various contributions of nociceptive processes to stimulus processing can be observed. To observe the responsiveness of nociceptive thresholds to changes in nociceptive function, a model of capsaicin-induced nerve defunctionalization was used. Its effect on nociceptive detections thresholds was investigated over a period of 84 days. A cutaneous capsaicin (8 %) patch was applied for 60 min to the upper leg of eight healthy human participants. Single- and double-pulse electrical stimuli were presented in a pseudo-random order using an intra-epidermal electrode. Stimuli and corresponding responses were recorded on both treated and untreated skin areas prior to capsaicin application and on days 2, 7, 28, and 84. Increases in electrical detection thresholds at the capsaicin area were observed on days 2 and 7 for single-pulse stimuli. Detection thresholds corresponding to double-pulse stimuli were increased on days 7 and 28, suggesting a delayed and longer lasting effect on double-pulse stimuli. In the present study, it was demonstrated that the responsiveness of detection thresholds to capsaicin application depends on the temporal properties of electrical stimuli. The observation of capsaicin-induced changes by estimation of detection thresholds revealed different time patterns of contributions of peripheral and central mechanisms to stimulus processing.

The Effect of Disruption of Prefrontal Cortical Function with Transcranial Magnetic Stimulation on Visual Working Memory.

It is proposed that feedback signals from the prefrontal cortex (PFC) to extrastriate cortex are essential for goal-directed processing, maintenance, and selection of information in visual working memory (VWM). In a previous study, we found that disruption of PFC function with transcranial magnetic stimulation (TMS) in healthy individuals impaired behavioral performance on a face/scene matching task and decreased category-specific tuning in extrastriate cortex as measured with functional magnetic resonance imaging (fMRI). In this study, we investigated the effect of disruption of left inferior frontal gyrus (IFG) function on the fidelity of neural representations of two distinct information codes: (1) the stimulus category and (2) the goal-relevance of viewed stimuli. During fMRI scanning, subjects were presented face and scene images in pseudo-random order and instructed to remember either faces or scenes. Within both anatomical and functional regions of interest (ROIs), a multi-voxel pattern classifier was used to quantitatively assess the fidelity of activity patterns representing stimulus category: whether a face or a scene was presented on each trial, and goal relevance, whether the presented image was task relevant (i.e., a face is relevant in a “Remember Faces” block, but irrelevant in a “Remember Scenes” block). We found a reduction in the fidelity of the stimulus category code in visual cortex after left IFG disruption, providing causal evidence that lateral PFC modulates object category codes in visual cortex during VWM. In addition, we found that IFG disruption caused a reduction in the fidelity of the goal relevance code in a distributed set of brain regions. These results suggest that the IFG is involved in determining the task-relevance of visual input and communicating that information to a network of regions involved in further processing during VWM. Finally, we found that participants who exhibited greater fidelity of the goal relevance code in the non-disrupted right IFG after TMS performed the task with the highest accuracy.

Interacting Effects of Instructions and Presentation Rate on Visual Statistical Learning.

The statistical regularities of a sequence of visual shapes can be learned incidentally. Arciuli et al. (2014) recently argued that intentional instructions only improve learning at slow presentation rates as they favor the use of explicit strategies. The aim of the present study was (1) to test this assumption directly by investigating how instructions (incidental vs. intentional) and presentation rate (fast vs. slow) affect the acquisition of knowledge and (2) to examine how these factors influence the conscious vs. unconscious nature of the knowledge acquired. To this aim, we exposed participants to four triplets of shapes, presented sequentially in a pseudo-random order, and assessed their degree of learning in a subsequent completion task that integrated confidence judgments. Supporting Arciuli et al.’s (2014) claim, participant performance only benefited from intentional instructions at slow presentation rates. Moreover, informing participants beforehand about the existence of statistical regularities increased their explicit knowledge of the sequences, an effect that was not modulated by presentation speed. These results support that, although visual statistical learning can take place incidentally and, to some extent, outside conscious awareness, factors such as presentation rate and prior knowledge can boost learning of these regularities, presumably by favoring the acquisition of explicit knowledge.

The incremental stimulus intensity effect in the habituation of the eyeblink response in humans

Investigation of the eyeblink response of humans to auditory and tactile stimulation focused on the determinants of the so called incremental stimulus intensity effect. In Experiment 1, two groups of participants were exposed to 100 tones from 60 to 87-dB in intensity. In Group Incremental, the tones increased from 60- to 87-dB in 3-dB steps, whereas participants in Group Random received the same intensities in a pseudorandom order. The performance of the two groups was compared to Group Constant that received all 100 tones at 90-dB intensity and to a fourth group, named “Apparatus” that received no stimulation. In a subsequent testing block, the results indicated that there was less responding to a 90-dB tone in the Incremental than in the other three groups, which replicates the incremental stimulus intensity effect. The novel observation was that there was also significantly less responding in the Incremental than in the other three groups to an untrained tactile stimulus, suggesting that the differences between the conditions may have implicated differences in a more general sensitization, in addition to any differences in stimulus-specific habituation. Experiment 2 demonstrated that repetition of tones at a fixed intensity caused a decrease in responding to the tones, but also an increase in responding to a novel tactile stimulus, as compared to an untrained condition. These results are discussed in terms of the interpretation of the incremental stimulus intensity effect suggested by Davis and Wagner (1969) and the AESOP (Wagner & Brandon, 1989) treatment of habituation and sensitization.

The change of kinesthesia and olfactory function in patients with Parkinson's disease

position after unloading. In theDI paradigm they did not react to the unloading perturbation. Every subject executed 8 sets of 10 trials (RP 4 sets, DI 4 sets) with a pseudo-randomized order. Angular acceleration of the wrist joint was obtained by a second-order differential of wrist angular movement registered with an electro-goniometer. The damping ratio of the wrist oscillation could be obtained from the logarithmic decay (δ) between two adjacent flexion acceleration peaks (P(i) and P(i+ 1)) (Eqs. (1) and (2)). Pertaining to the degree of joint stiffness, Wd was assessed with the time interval between two flexion acceleration peaks (T(i+ 1) and T(i)) (Eq. (3)).

Human oscillatory activity in near-miss events.

Near-miss events are situations in which an action yields a negative result but is very close to being successful. They are known to influence behavior, especially in gambling scenarios. Previous neuroimaging studies have described an 'anomalous' activity of brain reward areas following these events. The goal of the present research was to study electrophysiological correlates of near-misses in the expectation and outcome phases. Electroencephalography was recorded while participants were playing a simplified version of a slot machine. Four possible outcomes (gain, near-miss, loss and no-information) were presented in a pseudorandom order to ensure fixed proportions. Results from the time-frequency analysis for the theta (4-8 Hz), alpha (9-13 Hz), low beta (15-22 Hz) and beta-gamma (25-35 Hz) frequency-bands presented larger power increases for wins and near-misses compared with losses. In the anticipation phase, power changes were lower than in the resolution phase. The current results are in agreement with previous studies showing that near-miss events recruit brain areas of the reward network. Likewise, the oscillatory activity in near-misses is very similar to the one elicited in the gain condition. In addition, present findings suggest that oscillatory activity in the expectation phase does not play a crucial role in near-miss events.

The specificity of neural responses to music and their relation to voice processing: An fMRI-adaptation study

Several studies have identified, using functional magnetic resonance imaging (fMRI), a region within the superior temporal gyrus that preferentially responds to musical stimuli. However, in most cases, significant responses to other complex stimuli, particularly human voice, were also observed. Thus, it remains unknown if the same neurons respond to both stimulus types, albeit with different strengths, or whether the responses observed with fMRI are generated by distinct, overlapping neural populations. To address this question, we conducted an fMRI experiment in which short music excerpts and human vocalizations were presented in a pseudo-random order. Critically, we performed an adaptation-based analysis in which responses to the stimuli were analyzed taking into account the category of the preceding stimulus. Our results confirm the presence of a region in the anterior STG that responds more strongly to music than voice. Moreover, we found a music-specific adaptation effect in this area, consistent with the existence of music-preferred neurons. Lack of differences between musicians and non-musicians argues against an expertise effect. These findings provide further support for neural separability between music and speech within the temporal lobe.

Multifaceted effects of noisy galvanic vestibular stimulation on manual tracking behavior in Parkinson's disease.

Parkinson’s disease (PD) is a neurodegenerative movement disorder that is characterized clinically by slowness of movement, rigidity, tremor, postural instability, and often cognitive impairments. Recent studies have demonstrated altered cortico-basal ganglia rhythms in PD, which raises the possibility of a role for non-invasive stimulation therapies such as noisy galvanic vestibular stimulation (GVS). We applied noisy GVS to 12 mild-moderately affected PD subjects (Hoehn and Yahr 1.5–2.5) off medication while they performed a sinusoidal visuomotor joystick tracking task, which alternated between 2 task conditions depending on whether the displayed cursor position underestimated the actual error by 30% (‘Better’) or overestimated by 200% (‘Worse’). Either sham or subthreshold, noisy GVS (0.1–10 Hz, 1/f-type power spectrum) was applied in pseudorandom order. We used exploratory (linear discriminant analysis with bootstrapping) and confirmatory (robust multivariate linear regression) methods to determine if the presence of GVS significantly affected our ability to predict cursor position based on target variables. Variables related to displayed error were robustly seen to discriminate GVS in all subjects particularly in the Worse condition. If we considered higher frequency components of the cursor trajectory as “noise,” the signal-to-noise ratio of cursor trajectory was significantly increased during the GVS stimulation. The results suggest that noisy GVS influenced motor performance of the PD subjects, and we speculate that they were elicited through a combination of mechanisms: enhanced cingulate activity resulting in modulation of frontal midline theta rhythms, improved signal processing in neuromotor system via stochastic facilitation and/or enhanced “vigor” known to be deficient in PD subjects. Further work is required to determine if GVS has a selective effect on corrective submovements that could not be detected by the current analyses.

Vowel generation for children with cerebral palsy using myocontrol of a speech synthesizer.

For children with severe cerebral palsy (CP), social and emotional interactions can be significantly limited due to impaired speech motor function. However, if it is possible to extract continuous voluntary control signals from the electromyograph (EMG) of limb muscles, then EMG may be used to drive the synthesis of intelligible speech with controllable speed, intonation and articulation. We report an important first step: the feasibility of controlling a vowel synthesizer using non-speech muscles. A classic formant-based speech synthesizer is adapted to allow the lowest two formants to be controlled by surface EMG from skeletal muscles. EMG signals are filtered using a non-linear Bayesian filtering algorithm that provides the high bandwidth and accuracy required for speech tasks. The frequencies of the first two formants determine points in a 2D plane, and vowels are targets on this plane. We focus on testing the overall feasibility of producing intelligible English vowels with myocontrol using two straightforward EMG-formant mappings. More mappings can be tested in the future to optimize the intelligibility. Vowel generation was tested on 10 healthy adults and 4 patients with dyskinetic CP. Five English vowels were generated by subjects in pseudo-random order, after only 10 min of device familiarization. The fraction of vowels correctly identified by 4 naive listeners exceeded 80% for the vowels generated by healthy adults and 57% for vowels generated by patients with CP. Our goal is a continuous “virtual voice” with personalized intonation and articulation that will restore not only the intellectual content but also the social and emotional content of speech for children and adults with severe movement disorders.

Beyond P300: an auditory ERP paradigm with sequential stimulation

Event Abstract Back to Event Beyond P300: an auditory ERP paradigm with sequential stimulation Johannes Hoehne1* and Michael Tangermann2 1 Berlin Institute of Technology, Neurotechnology, Germany 2 University of Freiburg, Germany 1. Research Background: Brain-computer interfaces (BCIs) aim to establish communication channels which are independent of muscle movements, relying on the real-time analysis of brain signals instead. Typically, BCI paradigms which evaluate evoked potentials in the EEG follow the principles of the oddball paradigm with random sequences of target and non-target stimuli. We investigate whether this randomness can be removed, allowing a very user-friendly paradigm where the user knows the order of stimulation. 2. Methods We performed an EEG study with 10 subjects. The subjects listened to a rapid sequence (SOA=83,3ms) of 30 auditory stimuli with the task to attend to only one stimulus/letter. The spoken alphabet with each letter lasting 250 ms was used as stimuli, which were presented either in a pseudorandom order (condition 1) or in a sequential order (condition 2). 3. Results Despite the rapid stimulation sequence, we found that the oddball paradigm (condition 1) elicited typical class-discriminative ERP components, such as N200 and P300. The evoked potentials in the sequential condition also showed class discriminant features, such that the EEG signature from attended stimuli was different from non-attended stimuli. However Figure 1 depicts that the ERPs from the sequential condition were clearly distinct from those components observed in the oddball condition, since they were lacking N200 and P300 components. 4. Conclusions Striving for the simplest-possible setup, we describe that one can also remove any randomness from an ERP-based BCI paradigm, by presenting 30 characters which are presented in a fix sequential order. We find that this paradigm - called CharStreamer - also elicits class discriminant EEG features which were however different to an oddball paradigm as they were lacking N200 and P300 components. Keywords: Auditory Perception, EEG, ERP, Brain-Computer Interfacing, oddball, Sequential stimuli, non-randomly ordered stimulation Conference: XII International Conference on Cognitive Neuroscience (ICON-XII), Brisbane, Queensland, Australia, 27 Jul - 31 Jul, 2014. Presentation Type: Poster Topic: Cognition and Executive Processes Citation: Hoehne J and Tangermann M (2015). Beyond P300: an auditory ERP paradigm with sequential stimulation. Conference Abstract: XII International Conference on Cognitive Neuroscience (ICON-XII). doi: 10.3389/conf.fnhum.2015.217.00163 Copyright: The abstracts in this collection have not been subject to any Frontiers peer review or checks, and are not endorsed by Frontiers. They are made available through the Frontiers publishing platform as a service to conference organizers and presenters. The copyright in the individual abstracts is owned by the author of each abstract or his/her employer unless otherwise stated. Each abstract, as well as the collection of abstracts, are published under a Creative Commons CC-BY 4.0 (attribution) licence (https://creativecommons.org/licenses/by/4.0/) and may thus be reproduced, translated, adapted and be the subject of derivative works provided the authors and Frontiers are attributed. For Frontiers’ terms and conditions please see https://www.frontiersin.org/legal/terms-and-conditions. Received: 19 Feb 2015; Published Online: 24 Apr 2015. * Correspondence: Mr. Johannes Hoehne, Berlin Institute of Technology, Neurotechnology, Berlin, Germany, j.hoehne@tu-berlin.de Login Required This action requires you to be registered with Frontiers and logged in. To register or login click here. Abstract Info Abstract The Authors in Frontiers Johannes Hoehne Michael Tangermann Google Johannes Hoehne Michael Tangermann Google Scholar Johannes Hoehne Michael Tangermann PubMed Johannes Hoehne Michael Tangermann Related Article in Frontiers Google Scholar PubMed Abstract Close Back to top Javascript is disabled. Please enable Javascript in your browser settings in order to see all the content on this page.

Amplitude and frequency prediction in the translational vestibulo-ocular reflex.

The goal of this study was to assess the effect of amplitude and frequency predictability on the performance of the translational vestibulo-ocular reflex (tVOR). Eye movements were recorded in 5 subjects during continuous vertical translation that consisted of a series of segments with: 1) 3 amplitudes at constant frequency (2 Hz) or 2) 3 different frequencies (1.6, 2, 2.5 Hz). Stimulus changes were presented in a pseudo-random order. We found that there was little change in the tVOR immediately after an unexpected stimulus change, as if eye velocity were being driven more by an expectation based on previous steady-state motion than by current head translation. For amplitude transitions, only about 30% of the eventual response change was seen in the first half cycle. Similarly, a sudden change in translation frequency did not appear in eye velocity for 70 ms, compared to a 8 ms lag during similar yaw rotation. Finally, after a sudden large decrease in frequency, the eyes continued to track at the original higher frequency, resulting initially in an anti-compensatory tVOR acceleration. Our results elucidate further the complexity of the tVOR and show that motion prediction based on prior experience plays an important role in its response.

Touch satiety: differential effects of stroking velocity on liking and wanting touch over repetitions.

A slow, gentle caress of the skin is a salient hedonic stimulus. Low threshold, unmyelinated C-tactile afferents fire preferentially to this type of touch, where slow (<1 cm/s) and fast (>10 cm/s) stroking velocities produce lower firing frequencies and are rated as less pleasant. The current aim was to investigate how the experience of tactile pleasantness changes with repeated exposure (satiety to touch). A further aim was to determine whether tactile satiety varied with different stroking velocities. The experimental paradigm used a controlled brush stroke to the forearm that was delivered repeatedly for ∼50 minutes. In Experiment 1, brush strokes were administered at three different velocities (0.3 cm/s, 3 cm/s and 30 cm/s), which were presented in a pseudo-randomised order. In Experiment 2, brush strokes were applied using only one velocity (either 3 or 30 cm/s). After each stroke, the participants rated both subjective pleasantness (liking) and wanting (the wish to be further exposed to the same stimulus) for each tactile sensation. In Experiment 1, both pleasantness and wanting showed a small, but significant, decrease over repetitions during stroking at 3 cm/s only, where the mean values for pleasantness and wanting were similar. Conversely, slower (0.3 cm/s) and faster (30 cm/s) stroking showed no decrease in ratings over time, however pleasantness was rated higher than wanting. In Experiment 2, both pleasantness and wanting showed a significant decrease over repetitions for both applied velocities, with a larger decrease in ratings for stroking at 3 cm/s. In conclusion, satiety to touch occurred with a slow onset and progression, where pleasantness and wanting ratings to stroking at 3 cm/s were affected more than at the slower or faster velocities. Tactile satiety appears to differ compared to appetitive and olfactory satiety, because the hedonic and rewarding aspects of touch persist for some time.

FMRI of pain studies using laser-induced heat on skin with and without the loved one near the subject – a pilot study on 'love hurts'

The aims of this study are to image and investigate the areas of brain response to laser-induced heat pain, to analyse for any difference in the brain response when a subject is alone and when her loved one is present next to the MRI gantry. Pain stimuli was delivered using Th-YAG laser to four female subjects. Blood-Oxygenation-Level-Dependent (BOLD) fMRI experiment was performed using blocked design paradigm with five blocks of painful (P) stimuli and five blocks of non-painful (NP) stimuli arranged in pseudorandom order with an 18 seconds rest (R) between each stimulation phase. Brain images were obtained from 3T Philips Achieva MRI scanner using 32-channel SENSE head coil. A T1-weighted image (TR/TE/slice/FOV = 9ms/4ms/4mm slices/240×240mm) was obtained for verification of brain anatomical structures. An echo-planar-imaging sequence were used for the functional scans (TR/TE/slice/flip/FOV=2000ms/35ms/4mm slices/90°/220×220mm). fMRI data sets were analysed using SPM 8.0 involving preprocessing steps followed by t-contrast analysis for individuals and FFX analysis. In both with and without-loved-one conditions, neuronal responses were seen in the somatosensory gyrus, supramarginal gyrus, thalamus and insula regions, consistent with pain-related areas. FFX analysis showed that the presence of loved one produced more activation in the frontal and supramarginal gyrus during painful and non-painful stimulations compared to absence of a loved one. Brain response to pain is modulated by the presence of a loved one, causing more activation in the cognitive/emotional area i.e. 'love hurts'.