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Jason B Mattingley

Publications and source records attributed to Jason B Mattingley.

At least 19 recordsLinked to original sources
PubMed2006

Things that go bump in the right: the effect of unimanual activity on rightward collisions.

Patients with right parietal damage and spatial neglect ignore the leftward features of their environment - causing them to bump into the left-side of doorways. In contrast, the normal population shows a mild attentional bias towards the left. Self-report measures show more collisions to the right in everyday settings. We sought to obtain a quantitative measure of lateralised bumping in a laboratory setting. Participants (n=276) walked through a narrow doorway and the experimenter recorded collisions. To investigate the association between bumping and paper-and-pencil tests of pseudoneglect, a line bisection task was administered. Unilateral activation of the hemispheres has been found to ameliorate the effects of spatial neglect. We investigated the effect of activation by asking participants to move their left-, right- or both-hands as they walked. In the both hands condition, which acted as a baseline, there were more right bumps than left bumps. The rightward bias was exasperated when the left hand moved, presumably because this movement activated the right hemisphere. In contrast, there were more left bumps when the right hand moved. The results demonstrate that bumping is not random and that we collide with the right side more often. Biases in bumping, however, were not related to biases in line bisection. The effect of hand-movement demonstrates that bumping is brought about by an imbalance of activation between the hemispheres.

Adult↗
PubMed2006

Neural correlates of imagined and synaesthetic colours.

The experience of colour is a core element of human vision. Colours provide important symbolic and contextual information not conveyed by form alone. Moreover, the experience of colour can arise without external stimulation. For many people, visual memories are rich with colour imagery. In the unusual phenomenon of grapheme-colour synaesthesia, achromatic forms such as letters, words and numbers elicit vivid experiences of colour. Few studies, however, have examined the neural correlates of such internally generated colour experiences. We used functional magnetic resonance imaging (fMRI) to compare patterns of cortical activity for the perception of external coloured stimuli and internally generated colours in a group of grapheme-colour synaesthetes and matched non-synaesthetic controls. In a voluntary colour imagery task, both synaesthetes and non-synaesthetes made colour judgements on objects presented as grey scale photographs. In a synaesthetic colour task, we presented letters that elicited synaesthetic colours, and asked participants to perform a localisation task. We assessed the neural activity underpinning these two different forms of colour experience that occur in the absence of chromatic sensory input. In both synaesthetes and non-synaesthetes, voluntary colour imagery activated the colour-selective area, V4, in the right hemisphere. In contrast, the synaesthetic colour task resulted in unique activity for synaesthetes in the left medial lingual gyrus, an area previously implicated in tasks involving colour knowledge. Our data suggest that internally generated colour experiences recruit brain regions specialised for colour perception, with striking differences between voluntary colour imagery and synaesthetically induced colours.

Adolescent↗
PubMed2006

Impaired temporal resolution of visual attention and dopamine beta hydroxylase genotype in attention-deficit/hyperactivity disorder.

BACKGROUND: Dopamine beta hydroxylase (DbetaH) catalyzes the conversion of dopamine to noradrenaline. Attention-deficit/hyperactivity disorder (ADHD) has been associated with the A2 allele of a Taq I polymorphism of the DBH gene. Since catecholamines regulate visual attention, we examined whether participants with ADHD were impaired on a task requiring temporal attention and how DBH genotype influenced temporal attention in ADHD. METHODS: Thirty-seven children and adolescents with ADHD and 52 matched, normal control subjects participated. Participants were presented with two visual stimuli, separated in time by either 50, 100, or 200 milliseconds, and were asked to judge the temporal order of their onset. Genotypes for the Taq 1 polymorphism were available for 33 of the ADHD participants. RESULTS: Attention-deficit/hyperactivity disorder participants were more error prone than control subjects, particularly when stimuli were presented close together in time (i.e., at the 50 milliseconds asynchrony). Moreover, ADHD individuals homozygous for the A2 allele performed more poorly than those without this allele, and this difference was accentuated at the 50 milliseconds asynchrony. CONCLUSIONS: Attention-deficit/hyperactivity disorder participants have an impaired rate of perceptual processing for rapidly presented visual events. Deficits in the temporal resolution of visual attention in ADHD are associated with the A2 allele of the Taq I DBH polymorphism or another variant with which it is in linkage disequilibrium.

Adolescent↗
PubMed2006

Enhancement of visual selection during transient disruption of parietal cortex.

Selective attention is critical for guiding human behavior. Recent theories have described the process of attention as a biased competition between sensory inputs, but questions remain concerning the anatomical basis of these competitive mechanisms. Using transcranial magnetic stimulation, we found that disruption of the right parietal cortex improved the perception of relevant stimuli in competitive visual displays. This enhancement of selective attention is consistent with previous observations and suggests a crucial role of the superior parietal lobule and supramarginal gyrus in mediating competition between visual inputs.

Adolescent↗
PubMed2006

Synaesthesia: an overview of contemporary findings and controversies.

Research on synaesthesia is undergoing something of a renaissance, having initially been a hot topic in psychology and philosophy in the late 19th and early 20th centuries. One hundred years ago investigators failed to define an objective framework within which to characterise the phenomenon, and so interest in the topic waned. With the cognitive revolution and the rapid rise of new experimental techniques in human neuroscience, interest in synaesthesia as a legitimate topic for scientific investigation has been rekindled. Since the 1980s there has been rapid growth in scientific and media interest in synaesthesia, and there is now a sense that real progress is being made. This Special Issue of Cortex brings together the largest collection of empirical papers on the topic of synaesthesia to date. The 21 papers collected herein showcase the many significant advances that have been made in understanding the behavioural and neural bases of synaesthesia. The contributions reflect the work of more than 60 investigators from nine different countries. We are confident that the papers presented in this Special Issue will set the agenda for synaesthesia research for many years to come.

Association↗
PubMed2006

Attentional load attenuates synaesthetic priming effects in grapheme-colour synaesthesia.

One of the hallmarks of grapheme-colour synaesthesia is that colours induced by letters, digits and words tend to interfere with the identification of coloured targets when the two colours are different, i.e., when they are incongruent. In a previous investigation (Mattingley et al., 2001) we found that this synaesthetic congruency effect occurs when an achromatic-letter prime precedes a coloured target, but that the effect disappears when the letter is pattern masked to prevent conscious recognition of its identity. Here we investigated whether selective attention modulates the synaesthetic congruency effect in a letter-priming task. Fourteen grapheme-colour synaesthetes and 14 matched, non-synaesthetic controls participated. The amount of selective attention available to process the letter-prime was limited by having participants perform a secondary visual task that involved discriminating pairs of gaps in adjacent limbs of a diamond surrounding the prime. In separate blocks of trials the attentional load of the secondary task was systematically varied to yield 'low load' and 'high load' conditions. We found a significant congruency effect for synaesthetes, but not for controls, when they performed a secondary attention-demanding task during presentation of the letter prime. Crucially, however, the magnitude of this priming was significantly reduced under conditions of high-load relative to low-load, indicating that attention plays an important role in modulating synaesthesia. Our findings help to explain the observation that synaesthetic colour experiences are often weak or absent during attention-demanding tasks.

Adult↗
PubMed2006

Do synaesthetic colours act as unique features in visual search?

For individuals with grapheme-colour synaesthesia, letters, numbers and words elicit vivid and highly consistent colour experiences. A critical question in determining the mechanisms underlying the phenomenon is whether synaesthetic colours arise early in visual processing, prior to the allocation of focused attention, or at some later stage following explicit recognition of the inducing form. If the synaesthetic colour elicited by an achromatic target emerges early in visual processing, then the target should be relatively easy to find in an array of achromatic distractor items, provided the target and distractors elicit different synaesthetic colours. Here we present data from 14 grapheme-colour synaesthetes and 14 matched non-synaesthetic controls, each of whom performed a visual search task in which a target digit was distinguished from surrounding distractors either by its unique synaesthetic colour or by its unique display colour. Participants searched displays of 8, 16 or 24 items for a specific target. In the chromatic condition, target and distractor digits were presented in different colours (e.g., a yellow '2' amongst blue '5's). In the achromatic condition, all digits in the display were black, but targets elicited a different synaesthetic colour from that induced by the distractors. Both synaesthetes and controls showed the expected efficient (pop-out) search slopes when the target was defined by a unique display colour. In contrast, search slopes for both groups were equally inefficient when the target and distractors were achromatic, despite eliciting distinct colours for the synaesthetes under normal viewing conditions. These results indicate that, at least for the majority of individuals, synaesthetic colours do not arise early enough in visual processing to guide or attract focal attention. Our findings are consistent with the hypothesis that graphemic inducers must be selectively attended to elicit their synaesthetic colours.

Adolescent↗
PubMed2006

The effect of body and environment-centred coordinates on free-viewing perceptual asymmetries for vertical and horizontal stimuli.

Leftward and upward perceptual biases are commonly reported for horizontal and vertical stimuli, respectively. It is unclear, however, whether these biases are based upon body or environment-centred coordinates. Two experiments examined the contribution of these coordinate systems to free-viewing vertical and horizontal perceptual biases. In Experiment 1, normal participants (n = 35) made forced-choice luminance judgments on two mirror-reversed luminance gradients (the 'greyscales' task) presented in vertical and horizontal orientations. Body and environment-based coordinates were dissociated by tilting participants' heads to the left or right. A leftward and upward bias, which was observed in the horizontal and vertical conditions (respectively) when the head was upright, was extinguished when the head was tilted. Results indicated a dual reliance on body and environmental coordinates with some suggestion that the upward bias was more dependent on environmental coordinates. In Experiment 2 the same stimuli were presented as participants (n = 24) adopted an upright or supine pose. Once again, leftward and upward biases were observed in the upright condition. The leftward bias persisted in the supine condition whereas the upward bias was eliminated. Results demonstrate that the leftward bias is based predominantly on body coordinates whereas the upward bias is reliant on environmental/gravitational coordinates. The possibility that the neural basis for the biases lies in the inter-modal centres of the intraparietal region of the right hemisphere is discussed.

Adolescent↗
PubMed2006

Executive "brake failure" following deactivation of human frontal lobe.

In the course of daily living, humans frequently encounter situations in which a motor activity, once initiated, becomes unnecessary or inappropriate. Under such circumstances, the ability to inhibit motor responses can be of vital importance. Although the nature of response inhibition has been studied in psychology for several decades, its neural basis remains unclear. Using transcranial magnetic stimulation, we found that temporary deactivation of the pars opercularis in the right inferior frontal gyrus selectively impairs the ability to stop an initiated action. Critically, deactivation of the same region did not affect the ability to execute responses, nor did it influence physiological arousal. These findings confirm and extend recent reports that the inferior frontal gyrus is vital for mediating response inhibition.

Adolescent↗
PubMed2006

Stimulus- and goal-driven biases of selective attention following unilateral brain damage: implications for rehabilitation of spatial neglect and extinction.

In this review we address the question of whether selective attentional mechanisms within the ipsilesional field are intact in unilateral lesion patients with spatial neglect and extinction. We consider how a lesion-induced bias in the neural representation of salience critically disrupts the integration of goal-driven and stimulus-driven prioritization signals. This has important consequences for selectivity both within the 'impaired' contralesional field within the 'intact' ipsilesional field. Examples are drawn from the neuropsychological literature and recent experiments conducted within our own laboratory. The implications of ipsilesional spatial selection deficits for rehabilitation are discussed.

Attention↗
PubMed2005

Goal-driven selective attention in patients with right hemisphere lesions: how intact is the ipsilesional field?

Patients with right hemisphere (RH) lesions often display a spatial bias in attention towards the ipsilesional hemifield. The behavioural manifestations of this spatial bias are typically interpreted as reflecting increased or enhanced attention for stimuli within the 'intact' ipsilesional field, and impaired attentional functioning within the contralesional field. In the healthy brain, goal-driven and stimulus-driven attentional processes interact to determine which stimuli should be prioritized for selection. Although unilateral brain damage increases the relative attentional salience of stimuli within the ipsilesional field, it might also cause problems in filtering or attenuating task-irrelevant information. We examined whether goal-driven attention modulates the processing of ipsilesional and contralesional information in 6 patients with unilateral brain damage following RH stroke (5 male, 1 female; mean age 60.8 years) and a group of age and sex-matched controls. We used a flanker task in which participants made speeded judgements on a central target item (a coloured letter). On each trial the target was flanked by a coloured letter in the left and right hemifields. In separate blocks, participants were instructed to judge either the identity or the colour of the central target and to ignore the flankers. The flanker on one side could be congruent, incongruent or neutral with respect to the target, on either the letter or the colour dimension, whereas the flanker on the other side was always neutral on both dimensions. Healthy controls showed significant interference from incongruent flankers on either side. Crucially, however, this effect only occurred for the task-relevant dimension [F(2,10) = 24.60; P < 0.001]. For patients, however, both the task-relevant and task-irrelevant dimensions of ipsilesional flankers interfered with response times [task-relevant: F(2,10) = 7.50, P < 0.05; task-irrelevant: F(1,5) = 6.20, P < 0.05]. Conversely, contralesional flankers influenced response times only when the target and distractor were incongruent on the task-relevant dimension [F(2,10) = 4.85; P < 0.05]. Our findings demonstrate that following RH damage, goal-driven biases cannot constrain the processing of task-irrelevant features of ipsilesional stimuli. We speculate that a lateralized bias in spatial attention leads to unselective prioritization of all feature-based attributes of stimuli appearing within the ipsilesional hemifield, whether or not they are relevant to performance. Attentional selection for ipsilesional stimuli in disorders such as spatial neglect and extinction may not therefore be entirely normal, as previously assumed.

Aged↗
PubMed2005

Neurodisruption of selective attention: insights and implications.

Mechanisms of selective attention are vital for coherent perception and action. Recent advances in cognitive neuroscience have yielded key insights into the relationship between neural mechanisms of attention and eye movements, and the role of frontal and parietal brain regions as sources of attentional control. Here we explore the growing contribution of reversible neurodisruption techniques, including transcranial magnetic stimulation and microelectrode stimulation, to the cognitive neuroscience of spatial attention. These approaches permit unique causal inferences concerning the relationship between neural processes and behaviour, and have revealed fundamental mechanisms of attention in the human and animal brain. We conclude by suggesting that further advances in the neuroscience of attention will be facilitated by the combination of neurodisruption techniques with established neuroimaging methods.

Animals↗
PubMed2005

Simple metric for scaling motor threshold based on scalp-cortex distance: application to studies using transcranial magnetic stimulation.

Transcranial magnetic stimulation (TMS) is a unique method in neuroscience used to stimulate focal regions of the human brain. As TMS gains popularity in experimental and clinical domains, techniques for controlling the extent of brain stimulation are becoming increasingly important. At present, TMS intensity is typically calibrated to the excitability of the human motor cortex, a measure referred to as motor threshold (MT). Although TMS is commonly applied to nonmotor regions, most applications do not consider the effect of changes in distance between the stimulating device and underlying neural tissue. Here we show that for every millimeter from the stimulating coil, an additional 3% of TMS output is required to induce an equivalent level of brain stimulation at the motor cortex. This abrupt spatial gradient will have crucial consequences when TMS is applied to nonmotor regions because of substantial variance in scalp-cortex distances over different regions of the head. Stimulation protocols that do not account for cortical distance therefore risk substantial under- or overstimulation. We describe a simple method for adjusting MT to account for variations in cortical distance, thus providing a more accurate calibration than unadjusted MT for the safe and effective application of TMS in clinical and experimental neuroscience.

Adolescent↗
PubMed2005

Directed attention eliminates 'change deafness' in complex auditory scenes.

In natural environments that contain multiple sound sources, acoustic energy arising from the different sources sums to produce a single complex waveform at each of the listener's ears. The auditory system must segregate this waveform into distinct streams to permit identification of the objects from which the signals emanate [1]. Although the processes involved in stream segregation are now reasonably well understood [1, 2 and 3], little is known about the nature of our perception of complex auditory scenes. Here, we examined complex scene perception by having listeners detect a discrete change to an auditory scene comprising multiple concurrent naturalistic sounds. We found that listeners were remarkably poor at detecting the disappearance of an individual auditory object when listening to scenes containing more than four objects, but they performed near perfectly when their attention was directed to the identity of a potential change. In the absence of directed attention, this "change deafness" [4] was greater for objects arising from a common location in space than for objects separated in azimuth. Change deafness was also observed for changes in object location, suggesting that it may reflect a general effect of the dependence of human auditory perception on attention.

Adult↗
PubMed2005

Differential amygdala responses to happy and fearful facial expressions depend on selective attention.

Facial expressions of emotion elicit increased activity in the human amygdala. Such increases are particularly evident for expressions that convey potential threat to the observer, and arise even when the face is masked from awareness. We used functional magnetic resonance imaging (fMRI) to examine whether the amygdala responds differentially to threatening (fearful) versus nonthreatening (happy) facial expressions depending on whether the face is attended or actively ignored. In separate runs, participants were cued to attend to a face or a house within semitransparent, spatially overlaid composite pairs, presented either side of fixation, and were required to perform a demanding same/different judgment. We found significant attentional modulation of activity in category-specific 'face' (fusiform gyrus) and 'place' (parahippocampal gyrus) regions, with activity in each area increasing selectively when its preferred stimulus was attended versus ignored. In contrast, activity in the amygdala differed according to the valence of the facial expression and the category of the attended stimulus. For happy faces, activity in the amygdala was greater in the attend-face than in the attend-house condition, whereas for fearful faces, activity was greater in the attend-house than in the attend-face condition. We conclude that differential amygdala responses to fearful versus happy facial expressions are tuned by mechanisms of attention and that the amygdala gives preference to potentially threatening stimuli under conditions of inattention.

Adult↗
PubMed2005

Anarchic hand syndrome: bimanual coordination and sensitivity to irrelevant information in unimanual reaches.

Anarchic hand syndrome is characterised by unintended but purposeful and autonomous movements of the upper limb and intermanual conflict. Based on predictions of internal models of movement generation, we examined the role of visual cues in unimanual and bimanual movements in a patient with anarchic hand syndrome and in a matched control. In Experiment 1, participants made unimanual movements in a sequential button-pressing task. The cue for the next target in a sequence appeared either prior to (exogenous) or after (endogenous) the initiation of movement. For the patient, performance of the anarchic left hand was selectively impaired in the endogenous condition. In Experiment 2, participants made unimanual movements on a digitising tablet to a target, which appeared either alone or with a distractor. While the presence of a distractor was associated with increased Initiation time in general, the patient's anarchic left hand was particularly vulnerable to disruption by the distractor. The findings of Experiments 1 and 2 indicate excessive reliance on salient environmental stimuli for movement production in anarchic hand syndrome. We conclude that in AHS goal-directed actions of the affected limb are particularly vulnerable to disruption by non-relevant information. Finally, in Experiment 3, participants performed unimanual and mirror-image bimanual movements on a digitising tablet to targets in the left or right hemispace. Coupling of the parameters of the two hands was evident such that, compared with a unimanual baseline, Initiation time of the intact right hand deteriorated while it improved for the anarchic left hand.

Attention↗
PubMed2005

The effect of strategy on pseudoneglect for luminance judgements.

When judging the relative magnitude of the left and right sides of a stimulus, normal participants overestimate the leftward features (pseudoneglect). Although pseudoneglect and clinical neglect operate in opposite directions, the two phenomena may have a common cognitive and neural basis. For neglect, two strategies may be employed when inspecting horizontally aligned stimuli: (1) A global strategy where the stimuli are treated as a gestalt and asymmetries are detected or, (2) a comparison strategy where the qualities on the left and right sides of the stimuli are explicitly compared. To investigate the effect of these strategies on pseudoneglect, normal dextrals (n = 25 and 17) made two-alternative, forced-choice luminance discriminations between two mirror-reversed luminance gradients (greyscales). In an unseparated form, the stimuli are amenable to a global strategy. A comparison strategy was imposed by separating the stimuli into halves (Experiment 1) or quarters (Experiment 2). Despite the fact that the stimuli were equiluminant, participants predominantly chose the stimulus that was dark on the left as being darker overall in the unseparated condition. Response times were also faster for leftward responses. When the stimuli were separated into halves or quarters, the leftward bias was reduced, but not eliminated. The results demonstrate that both strategies contribute to pseudoneglect--though the global strategy may produce stronger pseudoneglect.

Adolescent↗