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1.  ‘Can you look me in the face?' Short-term SSRI Administration Reverts Avoidant Ocular Face Exploration in Subjects at Risk for Psychopathology 
Neuropsychopharmacology  2014;39(13):3059-3066.
Anxiety and depression are associated with altered ocular exploration of facial stimuli, which could have a role in the misinterpretation of ambiguous emotional stimuli. However, it is unknown whether a similar pattern is seen in individuals at risk for psychopathology and whether this can be modified by pharmacological interventions used in these disorders. In Study 1, eye gaze movement during face discrimination was compared in volunteers with high vs low neuroticism scores on the Eysenck Personality Questionnaire. Facial stimuli either displayed a neutral, happy, or fearful expression. In Study 2, volunteers with high neuroticism were randomized in a double-blind design to receive the selective serotonin reuptake inhibitor citalopram (20 mg) or placebo for 7 days. On the last day of treatment, eye gaze movement during face presentation and the recognition of different emotional expressions was assessed. In Study 1, highly neurotic volunteers showed reduced eye gaze towards the eyes vs mouth region of the face compared with low neurotic volunteers. In Study 2, citalopram increased gaze maintenance over the face stimuli compared with placebo and enhanced recognition of positive vs negative facial expressions. Longer ocular exploration of happy faces correlated positively with recognition of positive emotions. Individuals at risk for psychopathology presented an avoidant pattern of ocular exploration of faces. Short-term SSRI administration reversed this bias before any mood or anxiety changes. This treatment effect may improve the capacity to scan social stimuli and contribute to the remediation of clinical symptoms related to interpersonal difficulties.
PMCID: PMC4229577  PMID: 25035080
2.  Temporal expectation improves the quality of sensory information 
It is increasingly clear that we extract patterns of temporal regularity between events to optimize information processing. Whereas some of the mechanisms for facilitating action preparation and execution have been well documented, much less is understood about whether and how temporal expectations influence visual perception. We used a psychophysical paradigm and computational modeling to investigate the mechanisms by which temporal expectation can modulate visual perception. Visual targets appeared in a stream of noise-patches separated by a fixed (400-ms regular condition) or jittered (200/300/400/500/600-ms irregular condition) intervals. Targets were visual gratings tilted 45° clockwise or counter-clockwise, presented at one of seven contrast levels. Human observers were required to perform an orientation discrimination (i.e. left or right). Psychometric functions for contrast sensitivity fitted for the regular and irregular conditions indicated that temporal expectation modulates perceptual processing by enhancing the contrast sensitivity of visual targets. This increase in the signal strength was accompanied by a reduction in reaction times. A diffusion model indicated that rhythmic temporal expectation enhanced the signal-to-noise gain of the sensory evidence upon which decisions were made. These effects support the idea that attentional focus can entrain to the temporal structure of external events to optimize the processing of relevant sensory information.
PMCID: PMC4235252  PMID: 22699922
3.  Alpha oscillations related to anticipatory attention follow temporal expectations 
Temporal expectations have been shown to enhance visual analysis of task-relevant events, especially when these are coupled with spatial expectations. Oscillatory brain activity, particularly in the alpha band, has been implicated in regulating excitability in visual areas as a function of anticipatory spatial attention. Here we asked whether temporal expectations derived from regular, rhythmic events can modulate ongoing oscillatory alpha-band activity, so that the changes in cortical excitability are focused over the time intervals at which target events are expected. The task we used involved making a perceptual discrimination about a small target stimulus that reappeared from ‘behind’ a peripheral occluding band. Temporal expectations were manipulated by the regular, rhythmic versus irregular, arrhythmic approach of the stimulus toward the occluding band. Alpha-band activity was measured during the occlusion period, in which no stimulus was presented, but target reappearance was anticipated in conditions of high versus low temporal expectation. Time-frequency analysis showed that the amplitude of alpha-desynchronisation followed the time course of temporal expectations. Alpha desynchronisation increased rhythmically, peaking just before the expected reappearance of target times. Analysis of the event-related potentials evoked by the subsequent target stimuli showed enhancement of processing at both visual and motor stages. Our findings support a role for oscillations in regulating cortical excitability and suggest a plausible mechanism for biasing perception and action by temporal expectations.
PMCID: PMC4235253  PMID: 21976492
4.  Combining spatial and temporal expectations to improve visual perception 
Journal of Vision  2014;14(4):8.
The importance of temporal expectations in modulating perceptual functions is increasingly recognized. However, the means through which temporal expectations can bias perceptual information processing remains ill understood. Recent theories propose that modulatory effects of temporal expectations rely on the co-existence of other biases based on receptive-field properties, such as spatial location. We tested whether perceptual benefits of temporal expectations in a perceptually demanding psychophysical task depended on the presence of spatial expectations. Foveally presented symbolic arrow cues indicated simultaneously where (location) and when (time) target events were more likely to occur. The direction of the arrow indicated target location (80% validity), while its color (pink or blue) indicated the interval (80% validity) for target appearance. Our results confirmed a strong synergistic interaction between temporal and spatial expectations in enhancing visual discrimination. Temporal expectation significantly boosted the effectiveness of spatial expectation in sharpening perception. However, benefits for temporal expectation disappeared when targets occurred at unattended locations. Our findings suggest that anticipated receptive-field properties of targets provide a natural template upon which temporal expectations can operate in order to help prioritize goal-relevant events from early perceptual stages.
PMCID: PMC3983934  PMID: 24722562
temporal expectation; spatial expectation; synergistic effect; timing; visual attention
5.  Temporal expectation enhances contrast sensitivity by phase entrainment of low-frequency oscillations in visual cortex 
Although it is increasingly accepted that temporal expectation can modulate early perceptual processing, the underlying neural computations remain unknown. In the present study, we combined a psychophysical paradigm with electrophysiological recordings to investigate the putative contribution of low-frequency oscillatory activity in mediating the modulation of visual perception by temporal expectation. Human participants judged the orientation of brief targets (visual Gabor patterns tilted clockwise or counter-clockwise) embedded within temporally regular or irregular streams of noise-patches used as temporal cues. Psychophysical results indicated that temporal expectation enhanced the contrast sensitivity of visual targets. A diffusion model indicated that rhythmic temporal expectation modulated the signal-to-noise gain of visual processing. The concurrent electrophysiological data revealed that the phase of delta oscillations overlying human visual cortex (1 to 4 Hz) was predictive of the quality of target processing only in regular streams of events. Moreover, in the regular condition, the optimum phase of these perception-predictive oscillations occurred in anticipation of the expected events. Together, these results show a strong correspondence between psychophysical and neurophysiological data, suggesting that the phase entrainment of low-frequency oscillations to external sensory cues can serve as an important and flexible mechanism for enhancing sensory processing.
PMCID: PMC3638366  PMID: 23447609
6.  Endogenous modulation of low frequency oscillations by temporal expectations 
Journal of Neurophysiology  2011;106(6):2964-2972.
Recent studies have associated increasing temporal expectations with synchronization of higher frequency oscillations and suppression of lower frequencies. In this experiment, we explore a proposal that low-frequency oscillations provide a mechanism for regulating temporal expectations. We used a speeded Go/No-go task and manipulated temporal expectations by changing the probability of target presentation after certain intervals. Across two conditions, the temporal conditional probability of target events differed substantially at the first of three possible intervals. We found that reactions times differed significantly at this first interval across conditions, decreasing with higher temporal expectations. Interestingly, the power of theta activity (4–8 Hz), distributed over central midline sites, also differed significantly across conditions at this first interval. Furthermore, we found a transient coupling between theta phase and beta power after the first interval in the condition with high temporal expectation for targets at this time point. Our results suggest that the adjustments in theta power and the phase-power coupling between theta and beta contribute to a central mechanism for controlling neural excitability according to temporal expectations.
PMCID: PMC3234094  PMID: 21900508
temporal expectations; phase-power coupling; neural oscillations
7.  Behavioural Dissociation between Exogenous and Endogenous Temporal Orienting of Attention 
PLoS ONE  2011;6(1):e14620.
In the current study we compared the effects of temporal orienting of attention based on predictions carried by the intrinsic temporal structure of events (rhythm) and by instructive symbolic cues; and tested the degree of cognitive, strategic control that could be exerted over each type of temporal expectation. The experiments tested whether the distinction between exogenous and endogenous orienting made in spatial attention may extend to the temporal domain.
Task Design and Main Results
In this task, a ball moved across the screen in discrete steps and disappeared temporarily under an occluding band. Participants were required to make a perceptual discrimination on the target upon its reappearance. The regularity of the speed (rhythmic cue) or colour (symbolic cue) of the moving stimulus could predict the exact time at which a target would reappear after a brief occlusion (valid trials) or provide no temporal information (neutral trials). The predictive nature of rhythmic and symbolic cues was manipulated factorially in a symmetrical and orthogonal fashion. To test for the effects of strategic control over temporal orienting based on rhythmic or symbolic cues, participants were instructed either to “attend-to-speed” (rhythm) or “attend-to-colour”. Our results indicated that both rhythmic and symbolic (colour) cues speeded reaction times in an independent fashion. However, whilst the rhythmic cueing effects were impervious to instruction, the effects of symbolic cues were contingent on the instruction to attend to colour.
Final Conclusions
Taken together, our results provide evidence for the existence of qualitatively separable types of temporal orienting of attention, akin to exogenous and endogenous mechanisms.
PMCID: PMC3030556  PMID: 21297968
8.  Functionally dissociating temporal and motor components of response preparation in left intraparietal sulcus 
Neuroimage  2011;54(2-3):1221-1230.
To optimise speed and accuracy of motor behaviour, we can prepare not only the type of movement to be made but also the time at which it will be executed. Previous cued reaction-time paradigms have shown that anticipating the moment in time at which this response will be made (“temporal orienting”) or selectively preparing the motor effector with which an imminent response will be made (motor intention or “motor orienting”) recruits similar regions of left intraparietal sulcus (IPS), raising the possibility that these two preparatory processes are inextricably co-activated. We used a factorial design to independently cue motor and temporal components of response preparation within the same experimental paradigm. By differentially cueing either ocular or manual response systems, rather than spatially lateralised responses within just one of these systems, potential spatial confounds were removed. We demonstrated that temporal and motor orienting were behaviourally dissociable, each capable of improving performance alone. Crucially, fMRI data revealed that temporal orienting activated the left IPS even if the motor effector that would be used to execute the response was unpredictable. Moreover, temporal orienting activated left IPS whether the target required a saccadic or manual response, and whether this response was left- or right-sided, thus confirming the ubiquity of left IPS activation for temporal orienting. Finally, a small region of left IPS was also activated by motor orienting for manual, though not saccadic, responses. Despite their functional independence therefore, temporal orienting and manual motor orienting nevertheless engage partially overlapping regions of left IPS, possibly reflecting their shared ontogenetic roots.
Research Highlights
►Anticipating when and how to respond can be functionally and neurally dissociated. ►Temporal orienting (when) engages left IPS for both oculomotor and manual responses. ►Motor orienting (how) engages left IPS only for manual, not oculomotor, responses. ►Manual action circuits may be functionally recycled for anticipating when to respond.
PMCID: PMC3025354  PMID: 20868756
Motor attention; Motor preparation; Motor intention; Temporal preparation; Supramarginal gyrus
9.  Fornix microstructure correlates with recollection but not familiarity memory 
The fornix is the main tract between the medial temporal lobe (MTL) and medial diencephalon, both of which are critical for episodic memory. The precise involvement of the fornix in memory, however, has been difficult to ascertain since damage to this tract in human amnesics is invariably accompanied by atrophy to surrounding structures. We used diffusion-weighted imaging to investigate whether individual differences in fornix white matter microstructure in neurologically healthy participants were related to differences in memory as assessed by two recognition tasks. Higher microstructural integrity in the fornix tail was found to be associated with significantly better recollection memory. In contrast, there was no significant correlation between fornix microstructure and familiarity memory or performance on two non-mnemonic tasks. Our findings support the idea that there are distinct MTL-diencephalon pathways that subserve differing memory processes.
PMCID: PMC2825810  PMID: 19940194
Recognition Memory; Fornix; Hippocampal function; Memory; Hippocampus; Imaging

Results 1-9 (9)