Explicit behavioral detection of visual changes develops without their implicit neurophysiological detectability

Change blindness is a failure of reporting major changes across consecutive images if separated, e.g., by a brief blank interval. Successful change detection across interrupts requires focal attention to the changes. However, findings of implicit detection of visual changes during change blindness have raised the question of whether the implicit mode is necessary for development of the explicit mode. To this end, we recorded the visual mismatch negativity (vMMN) of the event-related potentials (ERPs) of the brain, an index of implicit pre-attentive visual change detection, in adult humans performing an oddball-variant of change blindness flicker task. Images of 500 ms in duration were presented repeatedly in continuous sequences, alternating with a blank interval (either 100 ms or 500 ms in duration throughout a stimulus sequence). Occasionally (P = 0.2), a change (referring to color changes, omissions, or additions of objects or their parts in the image) was present. The participants attempted to explicitly (via voluntary button press) detect the occasional change. With both interval durations, it took 10–15 change presentations in average for the participants to eventually detect the changes explicitly in a sequence, the 500 ms interval only requiring a slightly longer exposure to the series than the 100 ms one. Nevertheless, prior to this point of explicit detectability, the implicit detection of the changes vMMN could only be observed with the 100 ms intervals. These findings of explicit change detection developing with and without implicit change detection may suggest that the two modes of change detection recruit independent neural mechanisms

Negative findings of the handwriting legibility effect: the explanatory role of spontaneous task-specific debiasing

Teachers’ assessments of students’ academic performance are susceptible to various cognitive biases. The evidence for higher grades given for legibly than illegibly handwritten texts—the handwriting legibility effect—is partially negative in the literature, however. Three explanations for the negative evidence could be offered. First, the variation in handwriting legibility could simply fail to implicitly affect the graders’ behaviour. Secondly, the graders could intuitively associate handwriting illegibility with males and legibility with females. The presumed males’ texts could thereby receive higher grades than females’ texts, hiding the handwriting legibility effect proper. Third, the graders could spontaneously and selectively inhibit the handwriting legibility effect. In the present experiment, forty second-year teacher students graded fifth-grade students’ handwritten test answers. The answers varied independently in content quality and handwriting legibility. Handwriting legibility did not measurably vary the grades. Nevertheless, handwriting legibility became gender-stereotyped and, at a trend level, varied grading confidence. However, the gender stereotypes were not measurably reflected in the grades. This set of findings is best explained by the participants’ spontaneous and selective inhibition of the handwriting legibility effect. Spontaneous task-specific debiasing may, therefore, explain at least some of the previous negative findings of this effect in the literature. </p

Electrophysiological evidence for change detection in speech sound patterns by anesthetized rats

Peer reviewe

Memory-Based Mismatch Response to Frequency Changes in Rats

Any occasional changes in the acoustic environment are of potential importance for survival. In humans, the preattentive detection of such changes generates the mismatch negativity (MMN) component of event-related brain potentials. MMN is elicited to rare changes (‘deviants’) in a series of otherwise regularly repeating stimuli (‘standards’). Deviant stimuli are detected on the basis of a neural comparison process between the input from the current stimulus and the sensory memory trace of the standard stimuli. It is, however, unclear to what extent animals show a similar comparison process in response to auditory changes. To resolve this issue, epidural potentials were recorded above the primary auditory cortex of urethane-anesthetized rats. In an oddball condition, tone frequency was used to differentiate deviants interspersed randomly among a standard tone. Mismatch responses were observed at 60–100 ms after stimulus onset for frequency increases of 5% and 12.5% but not for similarly descending deviants. The response diminished when the silent inter-stimulus interval was increased from 375 ms to 600 ms for +5% deviants and from 600 ms to 1000 ms for +12.5% deviants. In comparison to the oddball condition the response also diminished in a control condition in which no repetitive standards were presented (equiprobable condition). These findings suggest that the rat mismatch response is similar to the human MMN and indicate that anesthetized rats provide a valuable model for studies of central auditory processing

Atypical perceptual narrowing in prematurely born infants is associated with compromised language acquisition at 2 years of age

Peer reviewe

Brain responses to pitch changes in an acoustic environment in cats and rabbits

Brain responses to pitch changes were measured in cats and rabbits. Event-related potentials (ERPs) were recorded from the hippocampus (cats and rabbits), cerebellar cortex, and visual cortex (rabbits). Additionally, multiple-unit activity (MUA) was measured in rabbits from the same trials and through the same electrodes as the ERPs. Pitch changes were introduced by presenting pitch deviant tones (deviants) in a sequence of homogenous repeated tones (standards). Differences in ERPs to the deviants and those to the standards (MMN-like ERPs) were found in recordings from the hippocampus and cerebellar cortex but not from the visual cortex. They did not occur before 75 ms from tone onset. MMN-like MUA was, in tum, present within the 20 ms latency in the hippocampus. The MMN-like responses reflected the different presentation rates of the deviants and standards only. Therefore, the responses did not resemble the mismatch negativity (MMN) observed in the cerebral cortex in humans and thought to represent a comparison process detecting a mismatch between a sensory input by the deviant and a short-term memory trace of the preceding standards. The hippocampal MUA recordings revealed a fast (latency less than 20 ms) increase in spike activity, particularly to the standards, suggesting that the higher stimulus presentation rate did not result in refractoriness on the part of those neural ensembles that were activated by the stimulation, as has been proposed in the case of the reduced amplitude of the Nl deflection of ERPs in humans. Three main conclusions can be drawn. First, instead of a separate comparison process, the different presentation rate of each type of stimulus per se is sufficient to explain the observed differences between responses to the deviants and those to the standards. Second, rather than neural refractoriness, this effect may represent an active process related to the formation of the short-term memory trace of repeated stimuli. Thirdly, since the effect of the stimulus repetition rate can be related to the memory trace, the trace seems to be widely distributed in the brain