Probe Stimuli Research Articles

Auditory working memory in noise in cochlear implant users: Insights from behavioural and neuronal measures.

We investigated auditory working-memory using behavioural measures and electroencephalography (EEG) in adult Cochlear Implant (CI) users with varying degrees of CI performance. 24 adult CI listeners (age: M = 61.38, SD = 12.45) performed the Sternberg auditory-digit-in-working-memory task during which EEG, accuracy, and promptness were captured. Participants were presented with 2, 4, or 6 digits at Signal-to-Noise Ratios (SNR) of 0, +5 and +10dB. They had to identify a probe stimulus as present in the preceding sequence. ANOVA models were used to compare conditions. ANOVA revealed that increasing memory load (ML) led to decreased task performance and CI performance interacted with ML and SNR. Centro-parietal alpha power increased during memory encoding but did not differ between conditions. Frontal alpha power was positively correlated with accuracy in conditions most affected by SNR (r = 0.57, r = 0.52) and theta power in conditions most affected by ML (r = 0.55, r = 0.57). While parietal alpha power is modulated by the task, it is frontal alpha that relates quantitatively to sensory aspects of processing (noise) and frontal theta to memory load in this group of CI listeners. These results suggest that alpha and theta show distinct relationships to behaviour, providing additional insight into neurocognitive (auditory working-memory) processes in CI users.

Effect of Level and Frequency of Forward Masker on Auditory Brainstem Response.

Forward masking (FM) is characterized by the perception of a signal being reduced or wholly masked due to a preceding sound (masker) of the same or different frequencies that offers a challenge for the auditory system to resolve. Considering that the off-frequency masker is expected to undergo linear processing compared to the on-frequency masker at the signal place, it reflects the peripheral auditory systems' compressive response. Thus, the present study focused on employing FM electrophysiological analogous such as auditory brainstem responses (ABR) to the behavioral masking experiments to objectively measure the frequency and level of processing in the auditory system, from the periphery to the brainstem level. The study was an observational research on 21 female volunteers. ABR was obtained using a tone-on-tone FM paradigm for 1000- and 4000-Hz probe stimuli. An experiment used two forward maskers, on-frequency and off-frequency, with varying levels from 50 to 70 dB SPL. A progressive shift for Vth peak latency and reduction in response amplitude was observed in proportion to the increase of masker level for both the probe stimuli and the masking experiments. However, ABR responses in neither masking condition were observed to differ between 60 and 70 dB SPL. FM ABR experiments are an assessment tool for estimating frequency and level processing in the auditory system, providing good efficiency, reliability, and less subject bias compared to behavioral measures.

Mapping punishment avoidance learning deficits in non-suicidal self-injury in young adults with and without borderline personality disorder: An fMRI study

IntroductionNon-suicidal self-injury (NSSI) is a growing public health concern among young adults in both clinical and non-clinical settings. Despite evidence linking NSSI to alterations in learning from reward and punishment, this area remains understudied, especially in non-clinical populations without borderline personality disorder (BPD). MethodsWe employed a modified version of the Probabilistic Stimulus Selection (PSS) task in two groups of young adults with recurrent NSSI, with (NSSI+BPD) and without BPD (NSSI), and an additional group of healthy controls (HC). While undergoing functional magnetic resonance imaging (fMRI), participants were asked to choose between pairs of stimuli with different reward probabilities. In the training phase, they received probabilistic feedback and learned to identify the most rewarding option within fixed pairs. In the test phase, these learned stimuli were recombined into novel pairs, where participants' accuracy in selecting the most rewarding and avoiding the most punishing options reflected their ability to learn from reward and punishment, respectively. ResultsCompared to HC, participants in the NSSI and NSSI+BPD groups were less accurate at avoiding the most punishing options than at choosing the most rewarding options, and showed reduced activity in the nucleus accumbens (NAcc) during punishment avoidance relative to reward selection. LimitationsThe modest sample size, descriptive rather than modeling approach, and absence of ecological momentary assessments may limit the results. ConclusionFindings suggest that reduced activation of the NAcc when avoiding loss may underlie difficulties in learning to avoid punishment in young adults with NSSI, regardless of the presence of BPD.

Application of the oddball paradigm for investigating predictive coding in the bat auditory system

Predictive coding is a theoretical framework for explaining how the auditory system efficiently codes the auditory scene by focusing on unexpected deviations. It is hypothesized that predictive coding plays a prominent role in the auditory processing of biosonar echo streams. At least two complementary biological mechanisms contribute to predictive coding: stimulus-specific adaptation (SSA), a reduced response to repetitive stimuli that emerges early in the ascending auditory pathway, and mismatch negativity (MMN), an enhanced response to low-probability stimuli mediated by the descending cortical feedback. Here, we utilized the oddball paradigm, an experimental design that measures the brain’s sensitivity to rare (deviant) stimuli, to detect and measure SSA and MMN in the auditory brainstem response (ABR) of anesthetized free-tailed bats. We predicted that SSA would be detectable in the early ABR peaks, and that MMN, if present, should appear in the slower P0 waves reflecting cortical influences on auditory expectations. Stimuli consisted of paired tones, FM sweeps, and other naturalistic stimuli, and we tested the effects of varying stimulus probabilities from 50/50 to 90/10. Results show that both SSA and MMN were detectable and separable even in early peaks of the ABR waveform.

Context-dependent neural preparation for information relevance vs. probability

Abstract Preparation is a top-down phenomenon known to improve performance across different situations. In light of recent electrophysiological findings that suggest that anticipatory neural preactivations linked to preparation are context-specific and do not generalize across domains, in the current study we used fMRI to investigate the brain regions involved in these differential patterns. We applied multivariate decoding to data obtained in a paradigm where, in different blocks, cues provided information about the relevance or probability of incoming target stimuli. Results showed that the anticipated stimulus category was pre-activated in both conditions, mostly in different brain regions within the ventral visual cortex and with differential overlap with actual target perception. Crucially, there was scarce cross-classification across attention and expectation contexts except on a patch of the fusiform gyrus, indicating mostly differential neural coding of anticipated contents in relevance and probability scenarios. Finally, a model-based fMRI-EEG fusion showed that these regions differentially code for specific conditions during preparation, as well as specifically preparing for category anticipation in a ramping-up manner. Overall, our results stress the specificity of anticipatory neural processing depending on its informative role while highlighting a key hub of commonality in the fusiform gyrus.

Stochastic electrical stimulation of the thoracic or cervical regions with surface electrodes facilitates swallow in rats.

Aspiration pneumonia, a leading cause of mortality, poses an urgent challenge in contemporary society. Neuromuscular electrical stimulation (NMES) has been commonly used in dysphagia rehabilitation. However, given that NMES at motor threshold targets only specific muscles, it carries a potential risk of further compromising functions related to swallowing, respiration, and airway protection. Considering that the swallow motor pattern is orchestrated by the entire swallow pattern generator (the neural mechanism governing a sequence of swallow actions), a rehabilitation approach that centrally facilitates the entire circuit through sensory nerve stimulation is desirable. In this context, we propose a novel stimulation method using surface electrodes placed on the back to promote swallowing. The efficacy of the proposed method in promoting swallowing was evaluated by electrically stimulating sensory nerves in the back or neck. Probabilistic stimulus was applied to either the back or neck of male and female rats. Swallows were evoked by an oral water stimulus, and electromyographic (EMG) activity of the mylohyoid, thyroarytenoid, and thyropharyngeus muscles served as the primary outcome measure. Gaussian frequency stimulation applied to the skin surface of the thoracic back elicited significant increases in EMG amplitude of all three swallow-related muscles. Neck stimulation elicited a significant increase in EMG amplitude of the thyroarytenoid during swallow, but not the mylohyoid or thyropharyngeus muscles. While the targeted thoracic spinal segments T9-T10 have been investigated for enhancing respiration, the promotion of swallowing through back stimulation has not been previously studied. Furthermore, this study introduces a new probabilistic stimulus based on Gaussian distribution. Probabilistic stimuli have been reported to excel in nerve stimulation in previous research. The results demonstrate that back stimulation effectively facilitated swallow more than neck stimulation and suggest potential applications for swallowing rehabilitation.

The late positive event-related potential component is time locked to the decision in recognition memory tasks

Two event-related potential (ERP) components are commonly observed in recognition memory tasks: the Frontal Negativity (FN400) and the Late Positive Component (LPC). These components are widely interpreted as neural correlates of familiarity and recollection, respectively. However, the interpretation of LPC effects is complicated by inconsistent results regarding the timing of ERP amplitude differences. There are also mixed findings regarding how LPC amplitudes covary with decision confidence. Critically, LPC effects have almost always been measured using fixed time windows relative to memory probe stimulus onset, yet it has not been determined whether LPC effects are time locked to the stimulus or the recognition memory decision. To investigate this, we analysed a large (n = 132) existing dataset recorded during recognition memory tasks with old/new decisions followed by post-decisional confidence ratings. We used ERP deconvolution to disentangle contributions to LPC effects (defined as differences between hits and correct rejections) that were time locked to either the stimulus or the vocal old/new response. We identified a left-lateralised parietal LPC effect that was time locked to the vocal response rather than probe stimulus onset. We also isolated a response-locked, midline parietal ERP correlate of confidence that influenced measures of LPC amplitudes at left parietal electrodes. Our findings demonstrate that, contrary to widespread assumptions, the LPC effect is time locked to the recognition memory decision and is best measured using response-locked ERPs. By extension, differences in response time distributions across conditions of interest may lead to substantial measurement biases when analysing stimulus-locked ERPs. Our findings highlight important confounding factors that further complicate the interpretation of existing stimulus-locked LPC effects as neural correlates of recollection. We recommend that future studies adopt our analytic approach to better isolate LPC effects and their sensitivity to manipulations in recognition memory tasks.

What Fechner could not do: Separating perceptual encoding and decoding with difference scaling.

A key question in perception research is how stimulus variations translate into perceptual magnitudes, that is, the perceptual encoding process. As experimenters, we cannot probe perceptual magnitudes directly, but infer the encoding process from responses obtained in a psychophysical experiment. The most prominent experimental technique to measure perceptual appearance is matching, where observers adjust a probe stimulus to match a target in its appearance along the dimension of interest. The resulting data quantify the perceived magnitude of the target in physical units of the probe, and are thus an indirect expression of the underlying encoding process. In this paper, we show analytically and in simulation that data from matching tasks do not sufficiently constrain perceptual encoding functions, because there exist an infinite number of pairs of encoding functions that generate the same matching data. We use simulation to demonstrate that maximum likelihood conjoint measurement (Ho, Landy, & Maloney, 2008; Knoblauch & Maloney, 2012) does an excellent job of recovering the shape of ground truth encoding functions from data that were generated with these very functions. Finally, we measure perceptual scales and matching data for White's effect (White, 1979) and show that the matching data can be predicted from the estimated encoding functions, down to individual differences.

Association between physical health and neurocognition in first-episode schizophrenia

IntroductionImpaired cognition is a core feature of schizophrenia that is evident early in the first episode and is frequently accompanied by compromised physical health. Although physical health confers benefits to cognition, it remains unclear whether physical activity, body mass index (BMI) and cardiorespiratory fitness are associated with neurocognition in first episode schizophrenia patients. The purpose of this study was to examine differences in stimulus categorization and motor response selection processes between first-episode schizophrenia patients compared to age-matched controls and explore associations between physical health and these stages of information processing.MethodsFourteen young adult patients receiving care following a first episode of psychosis and a matched sample of nonpsychiatric controls completed a visual oddball task from which the P3 and LRP (lateralized readiness potential) event-related potential (ERP) components were extracted to assess stimulus categorization and response selection processes, respectively. Physical activity, aerobic fitness, and BMI were correlated with ERP measures.ResultsCompared with controls, patients had lower physical activity levels and longer P3 and LRP latencies. Regardless of stimulus probability, patients had reduced accuracy and slower reaction times relative to controls. In patients, marginal associations were found between physical activity and P3 difference waveform amplitude, and BMI was negatively associated with parent P3 waveform amplitude.DiscussionThe present findings suggest that cognitive impairment in first-episode schizophrenia spans both stimulus- and response-related stages of information processing, and may be targeted through physical activity interventions.

Optimization of direct cortical stimulation using tibial versus median nerve sensory mapping during midline brain tumor resection: illustrative case.

During brain tumor resection, neurophysiological mapping and monitoring help surgeons locate, characterize, and functionally assess eloquent brain areas in real time. The selection of mapping and monitoring targets has implications for successful surgery. Here, the authors compare direct cortical stimulation (DCS) as suggested by median nerve (MN) with posterior tibial nerve (PTN) cortical sensory mapping (SM) during mesial lesion resection. Recordings from a 6-contact cortical strip served to generate an MN and a PTN sensory map, which indicated the strip was anterior to the central sulcus. Responses exhibited an amplitude gradient with no phase reversal (PR). DCS, elicited through a stimulus probe or contact(s) of the strip, yielded larger responses from the corresponding sensory mapped limb; that is, PTN SM resulted in larger lower limb muscle responses than those suggested by MN SM. SM of the MN and PTN is effective for localizing eloquent cortical areas wherein the PTN is favored in surgery for mesial cortical tumors. The recorded amplitude of the cortical somatosensory evoked potential is a valuable criterion for defining the optimal location for DCS, despite an absent PR. The pathway at risk dictates the specifics of SM, which subsequently defines the optimal location for DCS.

Spike synchrony as a measure of Gestalt structure

The function of spike synchrony is debatable: some researchers view it as a mechanism for binding perceptual features, others – as a byproduct of brain activity. We argue for an alternative computational role: synchrony can estimate the prior probability of incoming stimuli. In V1, this can be achieved by comparing input with previously acquired visual experience, which is encoded in plastic horizontal intracortical connections. V1 connectivity structure can encode the acquired visual experience in the form of its aggregate statistics. Since the aggregate statistics of natural images tend to follow the Gestalt principles, we can assume that V1 is more often exposed to Gestalt-like stimuli, and this is manifested in its connectivity structure. At the same time, the connectivity structure has an impact on spike synchrony in V1. We used a spiking model with V1-like connectivity to demonstrate that spike synchrony reflects the Gestalt structure of the stimulus. We conducted simulation experiments with three Gestalt laws: proximity, similarity, and continuity, and found substantial differences in firing synchrony for stimuli with varying degrees of Gestalt-likeness. This allows us to conclude that spike synchrony indeed reflects the Gestalt structure of the stimulus, which can be interpreted as a mechanism for prior probability estimation.

Sensory perception is a holistic inference process.

Sensory perception is widely considered an inference process that reflects the best guess of a stimulus feature based on uncertain sensory information. Here we challenge this reductionist view and propose that perception is rather a holistic inference process that operates not only at the feature but jointly across all levels of the representational hierarchy. We test this hypothesis in the context of a commonly used psychophysical matching task in which subjects are asked to report their perceived orientation of a test stimulus by adjusting a probe stimulus (method-of-adjustment). We introduce a holistic matching model that assumes that subjects' reports reflect an optimal match between the test and probe stimulus, both in terms of their inferred feature (orientation) and also their higher level representation (orientation category). Validation against several existing data sets demonstrates that the model accurately and comprehensively predicts subjects' response behavior and outperforms previous models both qualitatively and quantitatively. Moreover, the model generalizes to other feature domains and offers an alternative account for categorical color perception. Our results suggest that categorical effects in sensory perception are ubiquitous and can be parsimoniously explained as optimal behavior based on holistic sensory representations. (PsycInfo Database Record (c) 2024 APA, all rights reserved).

Searching near and far: The attentional template incorporates viewing distance.

According to theories of visual search, observers generate a visual representation of the search target (the "attentional template") that guides spatial attention toward target-like visual input. In real-world vision, however, objects produce vastly different visual input depending on their location: your car produces a retinal image that is 10 times smaller when it is parked 50 compared to 5 m away. Across four experiments, we investigated whether the attentional template incorporates viewing distance when observers search for familiar object categories. On each trial, participants were precued to search for a car or person in the near or far plane of an outdoor scene. In "search trials," the scene reappeared and participants had to indicate whether the search target was present or absent. In intermixed "catch-trials," two silhouettes were briefly presented on either side of fixation (matching the shape and/or predicted size of the search target), one of which was followed by a probe-stimulus. We found that participants were more accurate at reporting the location (Experiments 1 and 2) and orientation (Experiment 3) of probe stimuli when they were presented at the location of size-matching silhouettes. Thus, attentional templates incorporate the predicted size of an object based on the current viewing distance. This was only the case, however, when silhouettes also matched the shape of the search target (Experiment 2). We conclude that attentional templates for finding objects in scenes are shaped by a combination of category-specific attributes (shape) and context-dependent expectations about the likely appearance (size) of these objects at the current viewing location. (PsycInfo Database Record (c) 2024 APA, all rights reserved).

Contralateral delay activity and alpha lateralization reflect retinotopic and screen-centered reference frames in visual memory

The visual system represents objects in a lateralized manner, with contralateral cortical hemispheres responsible for left and right visual hemifields. This organization extends to visual short-term memory (VSTM), as evidenced by electrophysiological indices of VSTM maintenance: contralateral delay activity (CDA) and alpha-band lateralization. However, it remains unclear if VSTM represents object locations in gaze-centered (retinotopic) or screen-centered (spatiotopic) coordinates, especially after eye movements. In two experiments, participants encoded the colors of target objects and made a lateral saccade during the maintenance interval, thereby shifting the object’s location on the retina. A non-lateralized probe stimulus was then presented at the new fixation for a change detection task. The CDA maintained lateralization towards the target’s original retinotopic location, unaffected by subsequent saccades, and did not invert polarity even when a saccade brought that location into the opposite hemifield. We also found conventional alpha lateralization towards the target’s location before a saccade. After a saccade, however, alpha was lateralized towards the screen center regardless of the target’s original location, even in a control condition without any memory requirements. This suggests that post-saccadic alpha-band lateralization reflects attentional processes unrelated to memory, while pre- and post-saccade CDA reflect VSTM maintenance in a retinotopic reference frame.

Visual working memory resolution defined by figural complexity in kindergarten children.

Visual working memory (VWM) allows us to store and manipulate incoming visual information briefly. Information acquisition (i.e., encoding) accuracy is critical for VWM to function properly. The accuracy of very young children's VWM encoding has not been explained adequately in previous studies. Therefore, this study clarified it by manipulating the complexity of the visual stimuli and examining kindergarten children's performance in a recognition task. Furthermore, we examined the relationship between encoding accuracy and the 4- to 6-year-old children's individual traits in a subanalysis, as individual traits (such as IQ and attention to detail-a trait of autism spectrum disorder) reportedly affect VWM capacity. The results revealed that distinguishing between target and probe stimuli becomes more difficult as stimulus and discrimination complexity increase. In addition, this study results in narrow attention (attention to detail) that could contribute to VWM capacity saving if VWM capacity is sufficient. However, if the VWM's capacity is exceeded, the relationship with IQ, such as the simultaneous processing score, is strengthened. This study clarified the degree of accuracy of information retained by preschool children aged 4 to 6 years. In addition to providing basic knowledge about VWM, we believe the findings can be useful in education and other fields.

Contribution of TRPM8‐mediated activity to thermally‐evoked reflex blink

Purpose: To study the characteristics of reflex blink evoked by cold and heat stimulation of the ocular surface (OS), and to define the contribution of TRPM8 to the process.Methods: The orbicularis oculi muscle electromyography signal (OOemg) and the ocular surface temperature (OST; measured with a small thermoprobe placed on the cornea) were recorded in anaesthetised rats. OS temperature changes (ΔT) were induced by topical instillation of 20 μL drops of saline solution at different temperatures (15–50°C). ΔT and the area under the curve (AUC) and duration of the evoked OOemg signals were analysed before (control) and after topical treatment with the TRPM8 antagonist N‐(3‐aminopropyl)‐2‐[(3‐methylphenyl) methoxy] ‐N‐(2‐thienylmethyl) benzamide hydrochloride (AMTB; 1 mM).Results: Mild (−ΔT 0.1–5°C) and intense (−ΔT 5–15°C) cooling always evoked a reflex OOemg signal (probability = 1). AMTB significantly reduced the probability of cooling to evoke blink (probability = 0.26 and 0.57 for mild and intense cold stimuli, respectively; p < 0.001). OOemg AUC and duration were also significantly reduced by AMTB (p < 0.01). Probability of evoking OOemg signal by mild (ΔT 0.1–5°C) and intense (ΔT 5–15°C) OS heating was low (0.30 and 0.59 respectively), and their duration and AUC were significantly smaller than those evoked by cooling (p < 0.001). Although AMTB did not modify the probability of heating stimuli to evoke OOemg signals (0.17 and 0.57 for mild and intense heating, respectively), the duration of signals evoked by mild heating stimuli was significantly increased (p < 0.001).Conclusions: Cold stimuli applied to the ocular surface always evoked reflex EMG activity of the lid muscle. This ability of cooling stimuli to evoke reflex blink is mediated by TRPM8 channels, whose pharmacological blockade reduces both the probability to evoke the reflex blink and its amplitude.Support: PID2020‐115934RB‐I00 from DOI: MCIN/AEI/10.13039/50110001103; CIPROM/2021/48 from Generalitat Valenciana, Spain.

On the Mathematical Relationship Between Contextual Probability and N400 Amplitude.

Accounts of human language comprehension propose different mathematical relationships between the contextual probability of a word and how difficult it is to process, including linear, logarithmic, and super-logarithmic ones. However, the empirical evidence favoring any of these over the others is mixed, appearing to vary depending on the index of processing difficulty used and the approach taken to calculate contextual probability. To help disentangle these results, we focus on the mathematical relationship between corpus-derived contextual probability and the N400, a neural index of processing difficulty. Specifically, we use 37 contemporary transformer language models to calculate the contextual probability of stimuli from 6 experimental studies of the N400, and test whether N400 amplitude is best predicted by a linear, logarithmic, super-logarithmic, or sub-logarithmic transformation of the probabilities calculated using these language models, as well as combinations of these transformed metrics. We replicate the finding that on some datasets, a combination of linearly and logarithmically-transformed probability can predict N400 amplitude better than either metric alone. In addition, we find that overall, the best single predictor of N400 amplitude is sub-logarithmically-transformed probability, which for almost all language models and datasets explains all the variance in N400 amplitude otherwise explained by the linear and logarithmic transformations. This is a novel finding that is not predicted by any current theoretical accounts, and thus one that we argue is likely to play an important role in increasing our understanding of how the statistical regularities of language impact language comprehension.

Antidepressant Effects and Potential Targets of Deep Brain Stimulation

A serious health issue that affects people all over the world, severe depressive illness is linked to intricate neuronal circuits and neuromodulatory systems. Millions of people are affected by its increasing frequency, which places a heavy economic strain on society. Innovative methods are required because of the drawbacks of standard therapies, such as antidepressants and invasive operations. Deep brain stimulation has shown promise in the treatment of Major Depressive Disorder (MDD) since it is minimally invasive and has the opportunity for personalised care. Finding the best sites for deep brain stimulation is still difficult, though. Recent innovations, such brain biomarker-based Deep Brain Stimulation (DBS) device customization, offer fresh approaches to enhancing therapeutic effects. The present status of DBS for MDD is discussed in this study, with a focus on prospective target regions such the subcingulate colliculus (SCG), medial forebrain bundle (MFB), and bed nucleus of striatal terminal area (BNST). Modern methods like functional connectivity analysis and probabilistic stimulus mapping show probable brain regions linked to therapeutic improvement.

Sound reduces saccadic chronostasis illusion

The saccadic chronostasis illusion refers to the duration overestimation of the first visual stimulation after saccadic eye movement, which is also known as “stopped clock illusion.” The present study investigated whether saccadic chronostasis would be observed in the auditory modality and whether the saccade-induced time dilation in the visual modality would be reduced by a synchronously presented sound. In each trial, a unisensory visual stimulus, unisensory sound, or bimodal audio-visual stimulus with a duration of 200–800 ms (probe stimulus) was presented at the saccade target location and temporally around the offset of the saccade, followed by a unisensory visual or auditory standard stimulus for a fixed 500 ms. Participants were required to identify which of the two stimuli (probe or standard) presented in the target modality (visual or auditory) was perceived as longer. The results showed that no saccadic chronostasis was observed in the auditory modality, regardless of whether the sound was presented alone or synchronously accompanied by a visual stimulus. Interestingly, the magnitude of the saccadic chronostasis illusion was reduced by the synchronously presented sound. Moreover, the combined effect of the saccade and sound on visual time perception fits well with the standard scalar model, and the weight of the cross-modal effect was higher than that of saccadic visual time dilation. These results suggest that sound dominates vision in time processing during saccades and linearly modulates saccadic chronostasis, which follows the Scalar Expectancy Theory.

A power law describes the magnitude of adaptation in neural populations of primary visual cortex

How do neural populations adapt to the time-varying statistics of sensory input? We used two-photon imaging to measure the activity of neurons in mouse primary visual cortex adapted to different sensory environments, each defined by a distinct probability distribution over a stimulus set. We find that two properties of adaptation capture how the population response to a given stimulus, viewed as a vector, changes across environments. First, the ratio between the response magnitudes is a power law of the ratio between the stimulus probabilities. Second, the response direction to a stimulus is largely invariant. These rules could be used to predict how cortical populations adapt to novel, sensory environments. Finally, we show how the power law enables the cortex to preferentially signal unexpected stimuli and to adjust the metabolic cost of its sensory representation to the entropy of the environment.