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1.
Caffeine improves text reading and global perception.
Franceschini, S, Lulli, M, Bertoni, S, Gori, S, Angrilli, A, Mancarella, M, Puccio, G, Facoetti, A
Journal of psychopharmacology (Oxford, England). 2020;(3):315-325
Abstract
BACKGROUND Reading is a unique human skill. Several brain networks involved in this complex skill mainly involve the left hemisphere language areas. Nevertheless, nonlinguistic networks found in the right hemisphere also seem to be involved in sentence and text reading. These areas do not deal with phonological information, but are involved in verbal and nonverbal pattern information processing. The right hemisphere is responsible for global processing of a scene, which is needed for developing reading skills. AIMS Caffeine seems to affect global pattern processing specifically. Consequently, our aim was to discover if it could enhance text reading skill. METHODS In two mechanistic studies (n=24 and n=53), we tested several reading skills, global and local perception, alerting, spatial attention and executive functions, as well as rapid automatised naming and phonological memory, using a double-blind, within-subjects, repeated-measures design in typical young adult readers. RESULTS A single dose of 200 mg caffeine improved global processing, without any effect on local information processing, alerting, spatial attention and executive or phonological functions. This improvement in global processing was accompanied by faster text reading speed of meaningful sentences, whereas single word/pseudoword or pseudoword text reading abilities were not affected. These effects of caffeine on reading ability were enhanced by mild sleep deprivation. CONCLUSIONS These findings show that a small quantity of caffeine could improve global processing and text reading skills in adults.
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2.
Attention induced neural response trade-off in retinotopic cortex under load.
Torralbo, A, Kelley, TA, Rees, G, Lavie, N
Scientific reports. 2016;:33041
Abstract
The effects of perceptual load on visual cortex response to distractors are well established and various phenomena of 'inattentional blindness' associated with elimination of visual cortex response to unattended distractors, have been documented in tasks of high load. Here we tested an account for these effects in terms of a load-induced trade-off between target and distractor processing in retinotopic visual cortex. Participants were scanned using fMRI while performing a visual-search task and ignoring distractor checkerboards in the periphery. Retinotopic responses to target and distractors were assessed as a function of search load (comparing search set-sizes two, three and five). We found that increased load not only increased activity in frontoparietal network, but also had opposite effects on retinotopic responses to target and distractors. Target-related signals in areas V2-V3 linearly increased, while distractor response linearly decreased, with increased load. Critically, the slopes were equivalent for both load functions, thus demonstrating resource trade-off. Load effects were also found in displays with the same item number in the distractor hemisphere across different set sizes, thus ruling out local intrahemispheric interactions as the cause. Our findings provide new evidence for load theory proposals of attention resource sharing between target and distractor leading to inattentional blindness.
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3.
Gender and weight shape brain dynamics during food viewing.
Toepel, U, Knebel, JF, Hudry, J, le Coutre, J, Murray, MM
PloS one. 2012;(5):e36778
Abstract
Hemodynamic imaging results have associated both gender and body weight to variation in brain responses to food-related information. However, the spatio-temporal brain dynamics of gender-related and weight-wise modulations in food discrimination still remain to be elucidated. We analyzed visual evoked potentials (VEPs) while normal-weighted men (n = 12) and women (n = 12) categorized photographs of energy-dense foods and non-food kitchen utensils. VEP analyses showed that food categorization is influenced by gender as early as 170 ms after image onset. Moreover, the female VEP pattern to food categorization co-varied with participants' body weight. Estimations of the neural generator activity over the time interval of VEP modulations (i.e. by means of a distributed linear inverse solution [LAURA]) revealed alterations in prefrontal and temporo-parietal source activity as a function of image category and participants' gender. However, only neural source activity for female responses during food viewing was negatively correlated with body-mass index (BMI) over the respective time interval. Women showed decreased neural source activity particularly in ventral prefrontal brain regions when viewing food, but not non-food objects, while no such associations were apparent in male responses to food and non-food viewing. Our study thus indicates that gender influences are already apparent during initial stages of food-related object categorization, with small variations in body weight modulating electrophysiological responses especially in women and in brain areas implicated in food reward valuation and intake control. These findings extend recent reports on prefrontal reward and control circuit responsiveness to food cues and the potential role of this reactivity pattern in the susceptibility to weight gain.
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4.
The planning of a sequence of saccades in pro- and antisaccade tasks: influence of visual integration time and concurrent motor processing.
Lavergne, L, Vergilino-Perez, D, Collins, T, Orriols, E, Doré-Mazars, K
Brain research. 2008;:82-95
Abstract
Previous studies have shown that a saccade is coded in a specific reference frame according to its goal: to aim for a new object or to explore an object which has already been fixated. In a two saccade sequence, the second saccade aiming for a new object is programmed in a retinocentric reference frame in which the spatial location of the second object is stored in spatial memory before the first saccade and updated after its execution. The second saccade exploring the same object is coded in an oculocentric reference frame in which object size is directly transformed into a fixed motor vector, encoded in motor memory before the first saccade and simply applied after its execution. The integration of parafoveal visual information appears to be crucial in the selection of the appropriate reference frame. The two experiments presented here investigate how and when the saccadic system integrates visual information to plan a sequence of saccades. In separate blocks, subjects were asked to execute a sequence of prosaccades directed toward a single object or two short objects, or to execute a sequence of antisaccades in the opposite direction of the stimuli. The latency of the initial saccade was modulated by using the Gap-200, Gap-0 and Overlap-600 ms paradigms. The results show that the time available for segmenting the visual stimulation into discrete objects and application of a specific reference frame according to this segmentation is critical for saccadic planning.
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5.
Parvocellular and magnocellular contributions to the initial generators of the visual evoked potential: high-density electrical mapping of the "C1" component.
Foxe, JJ, Strugstad, EC, Sehatpour, P, Molholm, S, Pasieka, W, Schroeder, CE, McCourt, ME
Brain topography. 2008;(1):11-21
Abstract
The C1 component of the VEP is considered to index initial afference of retinotopic regions of human visual cortex (V1 and V2). C1 onsets over central parieto-occipital scalp between 45 and 60 ms, peaks between 70 and 100 ms, and then resolves into the following P1 component. By exploiting isoluminant and low-contrast luminance stimuli, we assessed the relative contributions of the Magnocellular (M) and Parvocellular (P) pathways to generation of C1. C1 was maximal at 88 ms in a 100% luminance contrast condition (which stimulates both P and M pathways) and at 115 ms in an isoluminant chromatic condition (which isolates contributions of the P pathway). However, in a 4% luminance contrast condition (which isolates the M pathway), where the stimuli were still clearly perceived, C1 was completely absent. Absence of C1 in this low contrast condition is unlikely to be attributable to lack of stimulus energy since a robust P1-N1 complex was evoked. These data therefore imply that C1 may be primarily parvocellular in origin. The data do not, however, rule out some contribution from the M system at higher contrast levels. Nonetheless, that the amplitude of C1 to P-isolating isoluminant chromatic stimuli is equivalent to that evoked by 100% contrast stimuli suggests that even at high contrast levels, the P system is the largest contributor. These data are related to intracranial recordings in macaque monkeys that have also suggested that the initial current sink in layer IV may not propagate effectively to the scalp surface when M-biased stimuli are used. We also discuss how this finding has implications for a long tradition of attention research that has used C1 as a metric of initial V1 afference in humans. C1 has been repeatedly interrogated for potential selective attentional modulations, particularly in spatial attentional designs, under the premise that modulation of this component, or lack thereof, would be evidence for or against selection at the initial inputs to visual cortex. Given the findings here, we would urge that in interpreting C1 effects, a consideration of the dominant cellular contributions will be necessary. For example, it is plausible that spatial attention mechanisms could operate primarily through the M system and that as such C1 may not always represent an adequate dependent measure in such studies.
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6.
A prospective study of change in visual function in patients treated with pegylated interferon alpha for hepatitis C in the UK.
Malik, NN, Sheth, HG, Ackerman, N, Davies, N, Mitchell, SM
The British journal of ophthalmology. 2008;(2):256-8
Abstract
BACKGROUND Hepatitis C virus and interferon treatment have been associated with retinopathy. Baseline and ongoing assessment by ophthalmologists have therefore been advocated in previous studies. Our experience suggests that the incidence is low, with no or negligible impact of pegylated interferon alpha on actual visual function. This study was conducted to determine whether ophthalmic assessment is necessary in such patients. METHODS The study was a prospective case series of 52 patients (104 eyes). Visual acuity, contrast sensitivity, colour vision, visual field by perimetry and fundal assessment were measured at baseline and at 3 and 6 months post commencement of interferon alpha treatment. RESULTS Forty-two men and ten women were followed. No patients reported any subjective visual symptoms. The mean changes in right and left logarithmic minimal angle resolution (LogMAR) visual acuity were negligible between baseline and 6 months (0.05 (SD 0.13) and 0.10 (SD 0.12), respectively). Mean changes in contrast sensitivity and colour vision were also negligible. Of all eyes monitored by serial perimetry for the full follow-up period and deemed to have reliable tests, none developed visual field defects. One patient appeared to develop nasal field defects within 3 months of commencing treatment but failed to attend for repeat testing. No patients developed optic disc changes or permanent fundal changes over the follow-up period. CONCLUSION In contrast to previous studies in America and south-east Asia, our findings based on a UK cohort suggest that routine ophthalmic screening is not essential for patients with hepatitis C treated with pegylated interferon alpha who have no subjective visual complaints.
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7.
Neural correlates of perceptual filling-in of an artificial scotoma in humans.
Weil, RS, Kilner, JM, Haynes, JD, Rees, G
Proceedings of the National Academy of Sciences of the United States of America. 2007;(12):5211-6
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Abstract
When a uniformly illuminated surface is placed eccentrically on a dynamic textured background, after a few seconds, it is perceived to disappear and be replaced by the background texture. Such texture filling-in is thought to occur in retinotopic visual cortex, but it has proven difficult to distinguish the contributions of invisible target and visible background to signals measured in these areas. Here, we used magnetoencephalography to measure time-dependent brain responses in human observers experiencing texture completion. We measured responses specifically associated with the filled-in target, by isolating neural population signals entrained at the frequency of flicker of the target. When perceptual completion occurred, and the target became invisible, there was significant reduction in the magnetoencephalography power at the target frequency over contralateral posterior sensors. However, even a subjectively invisible target nevertheless evoked frequency-specific signals compared with a no-target baseline. These data represent evidence for a persistent target-specific representation even for stimuli rendered invisible because of perceptual filling-in.
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8.
Effects of pharmacologically induced changes in NMDA receptor activity on human timing and sensorimotor performance.
Rammsayer, TH
Brain research. 2006;:407-16
Abstract
Unlike processing of time intervals in the range of seconds or more, processing of brief durations in the subsecond range appears to be beyond cognitive control and based on subcortical mechanisms located in the basal ganglia. The present study was designed to evaluate the effects of NMDA receptor activity on temporal processing in the second and subsecond range. In a double-blind crossover design, either 30 mg of the noncompetitive NMDA receptor antagonist memantine or placebo was administered to 32 healthy male volunteers. While memantine induced a marked impairment in temporal processing of intervals in the range of seconds, temporal processing of intervals in the range of milliseconds was not affected. Furthermore, no effect of memantine on speed of information processing could be observed. Speed of motor response execution, however, was significantly enhanced by memantine compared to placebo. The overall pattern of results provides converging evidence for the notion that temporal processing of longer intervals involves higher order working memory functions such as working memory capacity. The absence of an effect on temporal processing of very brief intervals in combination with the beneficial effect on movement time suggests that NMDA receptor activity in the basal ganglia is not directly related to the timing of intervals in the subsecond range.
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Effect of chronic caffeine intake on choice reaction time, mood, and visual vigilance.
Judelson, DA, Armstrong, LE, Sökmen, B, Roti, MW, Casa, DJ, Kellogg, MD
Physiology & behavior. 2005;(5):629-34
Abstract
The stimulatory effects of acute caffeine intake on choice reaction time, mood state, and visual vigilance are well established. Little research exists, however, on the effects of chronic caffeine ingestion on psychomotor tasks. Therefore, the purpose of this study was to evaluate the effects of 5 days of controlled caffeine intake on cognitive and psychomotor performance. Three groups of 20 healthy males (age=22+/-3 years, mass=75.4+/-7.9 kg, body fat percentage=11.2+/-5.1%) twice completed a battery of cognitive and psychomotor tasks: after 6 days of 3 mg.kg(-1) day(-1) caffeine equilibration (Day 6), and after 5 days of experimental (0 [G0], 3 [G3], or 6 [G6] mg.kg(-1) day(-1)) caffeine intake (Day 11). Groups were randomized and stratified for age, mass, and body composition; all procedures were double-blind. Cognitive analyses involved a visual four-choice reaction time test, a mood state questionnaire, and a visual vigilance task. Experimental chronic caffeine intake did not significantly alter the number of correct responses or the mean latency of response for either the four-choice reaction time or the visual vigilance tasks. The Vigor-Activity subset of the mood state questionnaire was significantly greater in G3 than G0 or G6 on Day 11. All other mood constructs were unaffected by caffeine intake. In conclusion, few cognitive and psychomotor differences existed after 5 days of controlled caffeine ingestion between subjects consuming 0, 3, or 6 mg.kg(-1) day(-1) of caffeine, suggesting that chronic caffeine intake (1) has few perceptible effects on cognitive and psychomotor well-being and (2) may lead to a tolerance to some aspects of caffeine's acute effects.
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10.
Caffeine restores engagement speed but not shooting precision following 22 h of active wakefulness.
Tikuisis, P, Keefe, AA, McLellan, TM, Kamimori, G
Aviation, space, and environmental medicine. 2004;(9):771-6
Abstract
BACKGROUND Current military missions occasionally require combat readiness of soldiers who might be experiencing a sustained period of activity without sleep. Strategies to overcome the debilitating effects of sleep deprivation include the ingestion of caffeine. Unknown is the efficacy of caffeine use on specific elements of target detection and marksmanship following a modest period of sustained wakefulness. METHODS There were 20 subjects (mean +/- SD of 26.7 +/- 7.2 yr of age, 179 +/- 6 cm in height, and 84.5 +/- 10.8 kg in weight) who participated in double-blind caffeine and placebo trials where each trial involved a 24-h control period (with sleep) followed by 22 h of mixed mental and physical activity with no sleep. At the end of this period, subjects engaged in a 1-h rifle-shooting task. Subjects ingested 400, 100, and 100 mg of caffeine or placebo at 7.5, 3, and 0 h, respectively, prior to shooting. Measures of shooting performance included target engagement time (between target appearance and firing), friend-foe discrimination, accuracy, and precision. RESULTS Most measures of performance were degraded in the placebo sleep-deprived condition, but only the target engagement time and the number of shots fired were restored by caffeine ingestion. CONCLUSIONS These findings concur with other research involving different periods of sleep deprivation, and indicate that the cognitive component of the shooting task (i.e., target detection) can benefit from caffeine whereas the psychomotor component (marksmanship) does not. It appears that once the target is detected, the subject is sufficiently aroused to engage the target regardless of the subject's level of alertness prior to detection.