Daniel Baker

University of York, Psychology, Faculty Member

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I completed a BSc in Psychology at the University of Nottingham in 2003. Following a year working outside academia, I moved to Birmingham to do a PhD at Aston university, under the supervision of Tim Meese. This project focussed on the binocular aspects of human contrast vision, such as dichoptic masking and binocular summation. During this period I also spent several months at McGill Vision Research Unit (Montreal) carrying out experiments on subjects with amblyopia. I was then employed for two years as a postdoc at Southampton University, followed by a further 3.5 years as a postdoc back at Aston. In January 2013 I started a lectureship at the University of York. For more details see: http://www.york.ac.uk/psychology/staff/faculty/daniel/

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Aurelio Bruno

University of York

Maarten van der Smagt

Derek Arnold

Inci Ayhan

Bogazici University, Istanbul, Turkey

Fondazione Santa Lucia

Myrka Zago

Thomas Ditye

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Papers by Daniel Baker

A purely visual adaptation to motion can differentiate between perceptual timing and interval timing

by Aurelio Bruno and Daniel Baker

Proceedings of the Royal Society B: Biological Sciences, 2023

It is unclear whether our brain extracts and processes time information using a single-centralize... more It is unclear whether our brain extracts and processes time information using a single-centralized mechanism or through a network of distributed mechanisms, which are specific for modality and time range. Visual adaptation has previously been used to investigate the mechanisms underlying time perception for millisecond intervals. Here, we investigated whether a well-known duration after-effect induced by motion adaptation in the sub-second range (referred to as 'perceptual timing') also occurs in the supra-second range (called 'interval timing'), which is more accessible to cognitive control. Participants judged the relative duration of two intervals after spatially localized adaptation to drifting motion. Adaptation substantially compressed the apparent duration of a 600 ms stimulus in the adapted location, whereas it had a much weaker effect on a 1200 ms interval. Discrimination thresholds after adaptation improved slightly relative to baseline, implying that the duration effect cannot be ascribed to changes in attention or to noisier estimates. A novel computational model of duration perception can explain both these results and the bidirectional shifts of perceived duration after adaptation reported in other studies. We suggest that we can use adaptation to visual motion as a tool to investigate the mechanisms underlying time perception at different time scales.

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A purely visual adaptation to motion can differentiate between perceptual timing and interval timing

by Aurelio Bruno and Daniel Baker

Proceedings of the Royal Society B: Biological Sciences, 2023

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Binaural summation of amplitude modulation involves weak interaural suppression

by Aurelio Bruno and Daniel Baker

Scientific Reports, 2020

The brain combines sounds from the two ears, but what is the algorithm used to achieve this summa... more The brain combines sounds from the two ears, but what is the algorithm used to achieve this summation of signals? Here we combine psychophysical amplitude modulation discrimination and steady-state electroencephalography (EEG) data to investigate the architecture of binaural combination for amplitude-modulated tones. Discrimination thresholds followed a 'dipper' shaped function of pedestal modulation depth, and were consistently lower for binaural than monaural presentation of modulated tones. The EEG responses were greater for binaural than monaural presentation of modulated tones, and when a masker was presented to one ear, it produced only weak suppression of the response to a signal presented to the other ear. Both data sets were well-fit by a computational model originally derived for visual signal combination, but with suppression between the two channels (ears) being much weaker than in binocular vision. We suggest that the distinct ecological constraints on vision and hearing can explain this difference, if it is assumed that the brain avoids over-representing sensory signals originating from a single object. These findings position our understanding of binaural summation in a broader context of work on sensory signal combination in the brain, and delineate the similarities and differences between vision and hearing.

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Binocular vision adaptively suppresses delayed monocular signals

NeuroImage, Jan 15, 2018

A neutral density filter placed before one eye will produce a dichoptic imbalance in luminance, w... more A neutral density filter placed before one eye will produce a dichoptic imbalance in luminance, which attenuates responses to visual stimuli and lags neural signals from retina to cortex in the filtered eye. When stimuli are presented to both the filtered and unfiltered eye (i.e., binocularly), neural responses show little attenuation and no lag compared with their baseline counterpart. This suggests that binocular visual mechanisms must suppress the attenuated and delayed input from the filtered eye; however, the mechanisms involved remain unclear. Here, we used a Steady-State Visual Evoked Potential (SSVEP) technique to measure neural responses to monocularly and binocularly presented stimuli while observers wore an ND filter in front of their dominant eye. These data were well-described by a binocular summation model, which received the sinusoidal contrast modulation of the stimulus as input. We incorporated the influence of the ND filter with an impulse response function, which ...

Dietary modulation of cortical excitation and inhibition

Journal of psychopharmacology (Oxford, England), 2017

The balance of excitatory and inhibitory neurotransmitters in the brain affects both neural respo... more The balance of excitatory and inhibitory neurotransmitters in the brain affects both neural responses and behaviour in humans and animals. Here we investigated whether dietary intervention aimed at increasing levels of the inhibitory neurotransmitter gamma-aminobutyric acid (GABA) can influence neural responses to basic sensory stimuli. Using a steady-state electroencephalography (EEG) paradigm, we found that the neural response to visual patterns was reduced in individuals who consumed a yeast extract product rich in substances associated with the production of GABA (glutamate and B vitamins), but not in a control group who consumed a placebo substance ( n = 14 per group). This demonstrates that the balance of excitation and inhibition in the brain can be influenced by dietary interventions, suggesting possible clinical benefits in conditions (e.g. epilepsy) where inhibition is abnormal.

Individual differences in internal noise are consistent across two measurement techniques

Vision research, Dec 22, 2016

Internal noise is a fundamental limiting property on visual processing. Internal noise has previo... more Internal noise is a fundamental limiting property on visual processing. Internal noise has previously been estimated with the equivalent noise paradigm using broadband white noise masks and assuming a linear model. However, in addition to introducing noise into the detecting channel, white noise masks can suppress neural signals, and the linear model does not satisfactorily explain data from other paradigms. Here we propose estimating internal noise from a nonlinear gain control model fitted to contrast discrimination data. This method, and noise estimates from the equivalent noise paradigm, are compared to a direct psychophysical measure of noise (double-pass consistency) using a detailed dataset with seven observers. Additionally, contrast discrimination and double-pass paradigms were further examined with a refined set of conditions in 40 observers. We demonstrate that the gain control model produces more accurate double-pass consistency predictions than a linear model. We also s...

Evidence for an Optimal Algorithm Underlying Signal Combination in Human Visual Cortex

Cerebral cortex (New York, N.Y. : 1991), Jan 27, 2016

How does the cortex combine information from multiple sources? We tested several computational mo... more How does the cortex combine information from multiple sources? We tested several computational models against data from steady-state electroencephalography (EEG) experiments in humans, using periodic visual stimuli combined across either retinal location or eye-of-presentation. A model in which signals are raised to an exponent before being summed in both the numerator and the denominator of a gain control nonlinearity gave the best account of the data. This model also predicted the pattern of responses in a range of additional conditions accurately and with no free parameters, as well as predicting responses at harmonic and intermodulation frequencies between 1 and 30 Hz. We speculate that this model implements the optimal algorithm for combining multiple noisy inputs, in which responses are proportional to the weighted sum of both inputs. This suggests a novel purpose for cortical gain control: implementing optimal signal combination via mutual inhibition, perhaps explaining its u...

Contrast and Lustre: a model that accounts for eleven different forms of contrast discrimination in binocular vision

Vision research, Dec 26, 2016

Our goal here is a more complete understanding of how information about luminance contrast is enc... more Our goal here is a more complete understanding of how information about luminance contrast is encoded and used by the binocular visual system. In two-interval forced-choice experiments we assessed observers' ability to discriminate changes in contrast that could be an increase or decrease of contrast in one or both eyes, or an increase in one eye coupled with a decrease in the other (termed IncDec). The base or pedestal contrasts were either in-phase or out-of-phase in the two eyes. The opposed changes in the IncDec condition did not cancel each other out, implying that along with binocular summation, information is also available from mechanisms that do not sum the two eyes' inputs. These might be monocular mechanisms. With a binocular pedestal, monocular increments of contrast were much easier to see than monocular decrements. These findings suggest that there are separate binocular (B) and monocular (L,R) channels, but only the largest of the three responses, max(L,B,R), ...

Grid-texture mechanisms in human vision: Contrast detection of regular sparse micro-patterns requires specialist templates

Scientific reports, Jul 27, 2016

Previous work has shown that human vision performs spatial integration of luminance contrast ener... more Previous work has shown that human vision performs spatial integration of luminance contrast energy, where signals are squared and summed (with internal noise) over area at detection threshold. We tested that model here in an experiment using arrays of micro-pattern textures that varied in overall stimulus area and sparseness of their target elements, where the contrast of each element was normalised for sensitivity across the visual field. We found a power-law improvement in performance with stimulus area, and a decrease in sensitivity with sparseness. While the contrast integrator model performed well when target elements constituted 50-100% of the target area (replicating previous results), observers outperformed the model when texture elements were sparser than this. This result required the inclusion of further templates in our model, selective for grids of various regular texture densities. By assuming a MAX operation across these noisy mechanisms the model also accounted for ...

Category-selective patterns of neural response in the ventral visual pathway in the absence of categorical information

NeuroImage, Jul 15, 2016

Neuroimaging studies have revealed distinct patterns of response to different object categories i... more Neuroimaging studies have revealed distinct patterns of response to different object categories in the ventral visual pathway. These findings imply that object category is an important organizing principle in this region of visual cortex. However, object categories also differ systematically in their image properties. So, it is possible that these patterns of neural response could reflect differences in image properties rather than object category. To differentiate between these alternative explanations, we used images of objects that had been phase-scrambled at a local or global level. Both scrambling processes preserved many of the lower-level image properties, but rendered the images unrecognizable. We then measured the effect of image scrambling on the patterns of neural response within the ventral pathway. We found that intact and scrambled images evoked distinct category-selective patterns of activity in the ventral stream. Moreover, intact and scrambled images of the same obj...

What Do Contrast Threshold Equivalent Noise Studies Actually Measure? Noise vs. Nonlinearity in Different Masking Paradigms

PloS one, 2016

The internal noise present in a linear system can be quantified by the equivalent noise method. B... more The internal noise present in a linear system can be quantified by the equivalent noise method. By measuring the effect that applying external noise to the system's input has on its output one can estimate the variance of this internal noise. By applying this simple "linear amplifier" model to the human visual system, one can entirely explain an observer's detection performance by a combination of the internal noise variance and their efficiency relative to an ideal observer. Studies using this method rely on two crucial factors: firstly that the external noise in their stimuli behaves like the visual system's internal noise in the dimension of interest, and secondly that the assumptions underlying their model are correct (e.g. linearity). Here we explore the effects of these two factors while applying the equivalent noise method to investigate the contrast sensitivity function (CSF). We compare the results at 0.5 and 6 c/deg from the equivalent noise method ag...

Short-term monocular patching boosts the patched eye’s response in visual cortex

by Mathieu Simard and Daniel Baker

Restorative Neurology and Neuroscience, 2015

Several recent studies have demonstrated that following short-term monocular deprivation in norma... more Several recent studies have demonstrated that following short-term monocular deprivation in normal adults, the patched eye, rather than the unpatched eye, becomes stronger in subsequent binocular viewing. However, little is known about the site and nature of the underlying processes. In this study, we examine the underlying mechanisms by measuring steady-state visual evoked potentials (SSVEPs) as an index of the neural contrast response in early visual areas. The experiment consisted of three consecutive stages: a pre-patching EEG recording (14 minutes), a monocular patching stage (2.5 hours) and a post-patching EEG recording (14 minutes; started immediately after the removal of the patch). During the patching stage, a diffuser (transmits light but not pattern) was placed in front of one randomly selected eye. During the EEG recording stage, contrast response functions for each eye were measured. The neural responses from the patched eye increased after the removal of the patch, whilst the responses from the unpatched eye remained the same. Such phenomena occurred under both monocular and dichoptic viewing conditions. We interpret this eye dominance plasticity in adult human visual cortex as homeostatic intrinsic plasticity regulated by an increase of contrast-gain in the patched eye.

Spatiotemporal Judgments of Observed Actions: Contrasts Between First- and Third-Person Perspectives After Motor Priming

Journal of experimental psychology. Human perception and performance, Jan 15, 2015

When observing actions, motor simulation processes aid the prediction and understanding of future... more When observing actions, motor simulation processes aid the prediction and understanding of future events. A central issue concerns whether such action simulation serves social functions of interpreting other people, where performance is predicted to be better when third-person perspective (3PP) actions are viewed, or whether it is most beneficial to guide self actions, whereby the first-person perspective (1PP) would be advantageous. We show that in a spatiotemporal judgment task there is an advantage for the prediction of 1PP. However, this is only detected after motor priming whereby participants perform the observed actions prior to making spatiotemporal judgments. The results, first, confirm that people draw on their motor experience for the accurate simulation and prediction of action. Second, the results suggest that such experience facilitates more accurate state estimation for actions perceived in the 1PP, which map more closely onto visual input of self-generated action. Mo...

Regarding the benefit of zero-dimensional noise

by Daniel Baker and Tim Meese

Journal of Vision, 2013

Unbiased measures of interocular transfer of motion adaptation

Perception, 44(5): 541-555

Numerous studies have measured the extent to which motion aftereffects transfer interocularly. Ho... more Numerous studies have measured the extent to which motion aftereffects transfer interocularly. However, many have done so using bias-prone methods, and studies rarely compare different types of motion directly. Here, we use a technique designed to reduce bias (Morgan, 2013, Journal of Vision, 13(8):26, 1–11) to estimate interocular transfer (IOT) for five types of motion: simple translational motion, expansion/contraction, rotation, spiral, and complex translational motion. We used both static and dynamic targets with subjects making binary judgments of perceived speed. Overall, the average IOT was 65%, consistent with previous studies (mean over 17 studies of 67% transfer). There was a main effect of motion type, with translational motion producing stronger IOT (mean: 86%) overall than any of the more complex varieties of motion (mean: 51%). This is inconsistent with the notion that IOT should be strongest for motion processed in extrastriate regions that are fully binocular. We conclude that adaptation is a complex phenomenon too poorly understood to make firm inferences about the binocular structure of motion systems.

Response to Davis and Plaisted-Grant: Psychophysical data do not support the low noise account of autism

Autism, 19(3): 365-366

Steady-state contrast response functions provide a sensitive and objective index of amblyopic deficits.

by Daniel Baker and Mathieu Simard

Investigative Ophthalmology & Visual Science, 56(2): 1208-1216

Purpose. Visual deficits in amblyopia are neural in origin, yet are difficult to characterize wit... more Purpose. Visual deficits in amblyopia are neural in origin, yet are difficult to characterize with functional magnetic resonance imagery (fMRI). Our aim was to develop an objective electroencephalography (EEG) paradigm that can be used to provide a clinically useful index of amblyopic deficits. Methods. We used steady-state visual evoked potentials (SSVEPs) to measure full contrast response functions in both amblyopic (n = 10, strabismic or mixed amblyopia, mean age: 44 years) and control (n = 5, mean age: 31 years) observers, both with and without a dichoptic mask. Results. At the highest target contrast, the ratio of amplitudes across the weaker and stronger eyes was highly correlated (r = 0.76) with the acuity ratio between the eyes. We also found that the contrast response function in the amblyopic eye had both a greatly reduced amplitude and a shallower slope, but that surprisingly dichoptic masking was weaker than in controls. The results were compared with the predictions of a computational model of amblyopia and suggest a modification to the model whereby excitatory (but not suppressive) signals are attenuated in the amblyopic eye. Conclusions. We suggest that SSVEPs offer a sensitive and objective measure of the ocular imbalance in amblyopia and could be used to assess the efficacy of amblyopia therapies currently under development.

Area summation of first- and second-order modulations of luminance

Journal of Vision, 15(1): 12, 1-13

To extend our understanding of the early visual hierarchy, we investigated the long-range integra... more To extend our understanding of the early visual hierarchy, we investigated the long-range integration of first- and second-order signals in spatial vision. In our first experiment we performed a conventional area summation experiment where we varied the diameter of (a) luminance-modulated (LM) noise and (b) contrast-modulated (CM) noise. Results from the LM condition replicated previous findings with sine-wave gratings in the absence of noise, consistent with long-range integration of signal contrast over space. For CM, the summation function was much shallower than for LM suggesting, at first glance, that the signal integration process was spatially less extensive than for LM. However, an alternative possibility was that the high spatial frequency noise carrier for the CM signal was attenuated by peripheral retina (or cortex), thereby impeding our ability to observe area summation of CM in the conventional way. To test this, we developed the “Swiss cheese” stimulus of Meese and Summers (2007) in which signal area can be varied without changing the stimulus diameter, providing some protection against inhomogeneity of the retinal field. Using this technique and a two-component subthreshold summation paradigm we found that (a) CM is spatially integrated over at least five stimulus cycles (possibly more), (b) spatial integration follows square-law signal transduction for both LM and CM and (c) the summing device integrates over spatially-interdigitated LM and CM signals when they are co-oriented, but not when cross-oriented. The spatial pooling mechanism that we have identified would be a good candidate component for a module involved in representing visual textures, including their spatial extent.

Thatcher’s Britain: a new take on an old illusion

Perception, 43(12): 1400-1403.

The Thatcher Illusion is generally discussed as a phenomenon related to face perception. Nonethel... more The Thatcher Illusion is generally discussed as a phenomenon related to face perception. Nonetheless, we show that compellingly strong Thatcher Effects can be elicited with nonface stimuli, provided that the stimulus set has a familiar standard configuration and a canonical view. Apparently, the Thatcher Illusion is not about faces, and nor is it about Thatcher. It just might, however, be about Britain.

Broadband noise masks suppress neural responses to narrowband stimuli

Frontiers in Psychology, 5: 763, Jul 15, 2014

White pixel noise is widely used to estimate the level of internal noise in a system by injecting... more White pixel noise is widely used to estimate the level of internal noise in a system by injecting external variance into the detecting mechanism. Recent work (Baker and Meese, 2012) has provided psychophysical evidence that such noise masks might also cause suppression that could invalidate estimates of internal noise. Here we measure neural population responses directly, using steady-state visual evoked potentials, elicited by target stimuli embedded in different mask types. Sinusoidal target gratings of 1 c/deg flickered at 5 Hz, and were shown in isolation, or with superimposed orthogonal grating masks or 2D white noise masks, flickering at 7 Hz. Compared with responses to a blank screen, the Fourier amplitude at the target frequency increased monotonically as a function of target contrast when no mask was present. Both orthogonal and white noise masks caused rightward shifts of the contrast response function, providing evidence of contrast gain control suppression. We also calculated within-observer amplitude variance across trials. This increased in proportion to the target response, implying signal-dependent (i.e., multiplicative) noise at the system level, the implications of which we discuss for behavioral tasks. This measure of variance was reduced by both mask types, consistent with the changes in mean target response. An alternative variety of noise, which we term zero-dimensional noise, involves trial-by-trial jittering of the target contrast. This type of noise produced no gain control suppression, and increased the amplitude variance across trials.

A purely visual adaptation to motion can differentiate between perceptual timing and interval timing

by Aurelio Bruno and Daniel Baker

Proceedings of the Royal Society B: Biological Sciences, 2023

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A purely visual adaptation to motion can differentiate between perceptual timing and interval timing

by Aurelio Bruno and Daniel Baker

Proceedings of the Royal Society B: Biological Sciences, 2023

Download

Binaural summation of amplitude modulation involves weak interaural suppression

by Aurelio Bruno and Daniel Baker

Scientific Reports, 2020

Download

Binocular vision adaptively suppresses delayed monocular signals

NeuroImage, Jan 15, 2018

Dietary modulation of cortical excitation and inhibition

Journal of psychopharmacology (Oxford, England), 2017

Individual differences in internal noise are consistent across two measurement techniques

Vision research, Dec 22, 2016

Evidence for an Optimal Algorithm Underlying Signal Combination in Human Visual Cortex

Cerebral cortex (New York, N.Y. : 1991), Jan 27, 2016

Contrast and Lustre: a model that accounts for eleven different forms of contrast discrimination in binocular vision

Vision research, Dec 26, 2016

Grid-texture mechanisms in human vision: Contrast detection of regular sparse micro-patterns requires specialist templates

Scientific reports, Jul 27, 2016

Category-selective patterns of neural response in the ventral visual pathway in the absence of categorical information

NeuroImage, Jul 15, 2016

What Do Contrast Threshold Equivalent Noise Studies Actually Measure? Noise vs. Nonlinearity in Different Masking Paradigms

PloS one, 2016

Short-term monocular patching boosts the patched eye’s response in visual cortex

by Mathieu Simard and Daniel Baker

Restorative Neurology and Neuroscience, 2015

Spatiotemporal Judgments of Observed Actions: Contrasts Between First- and Third-Person Perspectives After Motor Priming

Journal of experimental psychology. Human perception and performance, Jan 15, 2015

Regarding the benefit of zero-dimensional noise

by Daniel Baker and Tim Meese

Journal of Vision, 2013

Unbiased measures of interocular transfer of motion adaptation

Perception, 44(5): 541-555

Response to Davis and Plaisted-Grant: Psychophysical data do not support the low noise account of autism

Autism, 19(3): 365-366

Steady-state contrast response functions provide a sensitive and objective index of amblyopic deficits.

by Daniel Baker and Mathieu Simard

Investigative Ophthalmology & Visual Science, 56(2): 1208-1216

Area summation of first- and second-order modulations of luminance

Journal of Vision, 15(1): 12, 1-13

Thatcher’s Britain: a new take on an old illusion

Perception, 43(12): 1400-1403.

Broadband noise masks suppress neural responses to narrowband stimuli

Frontiers in Psychology, 5: 763, Jul 15, 2014

Daniel Baker

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