Theta Oscillation Related to the Auditory Discrimination Process in Mismatch Negativity: Oddball versus Control Paradigm

Background and Purpose

The aim of this study was to identify the mechanism underlying the auditory discriminatory process reflected in mismatch negativity (MMN), using time-frequency analysis of single-trial event-related potentials (ERPs).

Methods

Two auditory tones of different probabilities (oddball paradigm) and the same probability (control paradigm) were used. The average dynamic changes in amplitude were evaluated, and the in-phase consistency of the EEG spectrum at each frequency and time window across trials, event-related spectral perturbations (ERSPs), and inter-trial phase coherence (ITC) were computed.

Results

Subtraction of the ERPs of standard stimuli from the ERPs of deviant stimuli revealed a clear MMN component in the oddball paradigm. However, no discernible MMN component was observed in the control paradigm. Statistical tests showed that in the oddball paradigm, deviant tones produced significant increases of theta ERSPs and ITC at around 250 ms as compared with the standard tone, while no significant difference between the two stimuli was observed in the control paradigm.

Conclusions

Our results confirm that the auditory discriminatory process reflected in MMN is accompanied by phase resetting and power modulation at the theta frequency.     

Colour discrimination and categorisation in Williams syndrome

Individuals with Williams syndrome (WS) present with impaired functioning of the dorsal visual stream relative to the ventral visual stream. As such, little attention has been given to ventral stream functions in WS. We investigated colour processing, a predominantly ventral stream function, for the first time in nineteen individuals with Williams syndrome. Colour discrimination was assessed using the Farnsworth-Munsell 100 hue test. Colour categorisation was assessed using a match-to-sample test and a colour naming task. A visual search task was also included as a measure of sensitivity to the size of perceptual colour difference. Results showed that individuals with WS have reduced colour discrimination relative to typically developing participants matched for chronological age; performance was commensurate with a typically developing group matched for non-verbal ability. In contrast, categorisation was typical in WS, although there was some evidence that sensitivity to the size of perceptual colour differences was reduced in this group.     

Colour discrimination among patients with schizophrenia in Lebanon

Abstract

Background: Abnormalities and contrast sensitivity have already been studied in schizophrenia. However, the relationship between symptom severity in schizophrenia and colour vision sensitivity has not been studied systematically.

Aim: Our objective was to evaluate colour discrimination in patients with schizophrenia compared to controls and examine if this colour discrimination is correlated with schizophrenia symptoms’ severity.

Methods: This case–control study, performed between January and April 2017, included 50 schizophrenic patients and 50 healthy controls matched for age and sex. The Positive and Negative Symptoms Scale (PANSS) was used to determine the schizophrenia symptoms’ severity. Colour discrimination was evaluated using the total error score (TES) generated using the Farnsworth D-15 test. The higher the TES, the more severe colourblindness.

Results: A significantly higher mean TES was found in schizophrenics (30.32) compared to healthy patients (13.07) (p?<?0.001). Colour blindness was correlated to the severity of schizophrenic symptoms only in the subgroup of patients with severe schizophrenia.

Conclusion: Colour vision defect is a common feature in schizophrenia, and may be more significant when related to psychotic symptoms.

• KEY POINTS

• A significantly higher mean TES was found in schizophrenics compared to healthy patients.

• Colour blindness was correlated to the severity of schizophrenic symptoms only in the subgroup of patients with severe schizophrenia.

• Colour vision defect is a common feature in schizophrenia, and may be more significant when related to psychotic symptoms.

     

Event-Related Potentials for Gender Discrimination: An Examination Between Differences in Gender Discrimination Between Males and Females

The event-related potentials (ERP) following presentation of male and female faces were investigated to study differences in the gender discrimination process. Visual stimuli from four categories including male and female faces were presented. For the male subjects, the P220 amplitude of the T5 area following viewing of a female face was significantly larger than that following viewing of a male face. On the other hand for female subjects, the P170 amplitude of the Cz area following observation of a male face was larger than that for a female face. The results indicate that the neural processes, including responsive brain areas used for gender discrimination by observing faces, are different between males and females.     

Colour vision abnormalities and movement time in Parkinson's disease

Visual system dysfunction has been reported in Parkinson's disease (PD). The objective of the present study was to evaluate a putative association of distorted colour vision and delayed initiation and execution of movement in PD. We performed the Farnsworth-Munsell 100-hue test and estimated the total error score in 30 previously untreated parkinsonian patients and 30 age- and sex-matched controls. We then determined slowness in motor readiness and motor programming in the parkinsonian subjects on the same day. Subjects were asked to press a start button and release it after the randomized appearance of a visual stimulus and to move their right index finger to a reaction button as quickly as possible. Reaction time was considered as elapsed time between onset of the stimulus light and release of the start button, movement time was the time period between release of the start button and the pressing of the reaction button. Significant differences appeared between parkinsonian patients' and controls' reaction times (P = 0.007), movement time (P = 0.001) and total error score (P = 2.23E-08). A significant relation (Spearman R = 0.473, P = 0.008) was found between movement time and total error score, but not between reaction time and total error score (Spearman R = 0.259, P = 0.166). We conclude, that visual dysfunction and execution of movement are more influenced by altered dopaminergic neurotransmission in PD in comparison to the initiation of movement.     

Colour discrimination impairment is not a reliable early marker of Parkinson's disease

Disturbances of colour visual discrimination have been shown to occur frequently in Parkinson's disease (PD). To verify the potential utility of reduced colour sensitivity as a diagnostic marker of early PD, we examined 14 PD patients, mean age 55.4 years, disease duration 2.3 years, in Hoehn and Yahr stages 1, 1.5, or 2, previously untreated with levodopa. Colour discrimination was measured with the Farnsworth-Munsell 100-hue test in patients who were compared with age-matched controls. The examinations were performed under standard conditions in a room illuminated by a daylight lamp Biolux Osram 6500 K. The mean total error score (MTES) and partial error scores (green-yellow and red-green axis) were calculated for every person examined. No significant differences were found between PD patients (MTES 49.1 ± SD 37) and controls (MTES 37.9 ± SD 25). Similarly, the mean partial scores were not significantly elevated in PD patients. We found an elevation of error scores exceeding the upper limit of normality (control mean + 2SD) only in three patients. We conclude that colour visual discrimination is not consistently impaired in early stages of PD and does not appear as a reliable early marker of Parkinson's disease. Received: 26 September 2000, Received in revised form: 20 March 2001, Accepted: 28 March 2001     

Intact Behavioral Expression of Contextual Fear,Context Discrimination,and Object Discrimination Memories Acquired in the Absence of the Hippocampus

We test the hypothesis that the stability and precision of context and visual discrimination memories depend on interactions between the hippocampus (HPC) and other memory storage networks. In four experiments we tested the properties of memories acquired in the absence of the HPC. Long–Evans male rats were exclusively used in all experiments. Experiment 1 evaluated acquisition and retention of context fear memories in rats with prior partial or complete HPC damage. Confirming an earlier report (Zelikowsky et al., 2012) a very small but statistically reliable slowing in a single session of context fear conditioning was found after HPC damage. In contrast, retention of context fear memory was normal after HPC damage up to 30 d after learning. In experiment 2, we found that discrimination between a context paired with foot shocks and a different context never paired with foot shock was retained normally for 15 d. In experiment 3, we replicated the finding of intact context discrimination for at least 15 d in rats who display a significant impairment in acquisition of place learning in the Morris water task (MWT). In final experiment using an appetitive object discrimination task, we showed normal retention of the discrimination for at least 30 d after training in rats with complete HPC damage. These finding score against the idea that non HPC memory storage requires a period of interaction with HPC to establish a stable, precise memory.SIGNIFICANCE STATEMENT Contrary to expectations from systems memory consolidation, we find that in the absence of a functional hippocampus (HPC) context and visual memories are formed rapidly and exhibit normal persistence and precision. The findings suggest that the HPC is not obligatory for these features of long-term memories.     

Colour vision in juvenile myoclonic epilepsy

Aims. To determine the integrity of colour perception, related to photic sensitivity, in patients with juvenile myoclonic epilepsy. Methods. Twenty‐four patients with photoparoxysmal response, 27 patients without photoparoxysmal response, and 32 healthy individuals were investigated using the Farnsworth Munsell‐100 Hue test to calculate error scores for total colour, blue/yellow, and red/green. Results. No significant differences were observed regarding blue/yellow, red/green or total error score between juvenile myoclonic epilepsy patients with or without photoparoxysmal response. However, the data for all three scores were significantly higher in both patient groups compared to the healthy control group. In both patient groups, the blue/yellow error score was significantly higher than the red/green error score. Conclusions. We were unable to identify a relationship between photoparoxysmal response and colour vision in patients with juvenile myoclonic epilepsy. We believe that the underlying reason why juvenile myoclonic epilepsy patients had significantly higher blue/yellow, red/green, and total error score compared to the healthy control group may be due to GABA dysfunction, which is considered to play a role in the pathophysiology of this disease as well as the physiology of colour vision.     

Discrimination in health care against people with mental illness

This paper discusses factors associated with low rates of help-seeking and poorer quality of physical healthcare among people with mental illnesses. Evidence is reviewed on the associations between low rates of mental health literacy, negative attitudes towards people with mental illness, and reluctance to seek help by people who consider that they may have a mental disorder. People with mental illness often report encountering negative attitudes among mental health staff about their prognosis, associated in part with ‘physician bias’. ‘Diagnostic overshadowing’ appears to be common in general health care settings, meaning the misattribution of physical illness signs and symptoms to concurrent mental disorders, leading to underdiagnosis and mistreatment of the physical conditions.     

Skin Colour, Perception of Racism and Depression among Adolescents in Urban Brazil

Background: The relation between race, ethnicity and health has been recognised as having an important role in the understanding of social inequalities in health. In Brazil, miscegenation (the mixing of different ethnicities or races, especially in marriage) is recognised as a sign of racial tolerance, but individuals with black skin colour have poorer social and health indicators than whites. The hypothesis that perceived racial discrimination is associated with depression and depressive symptoms among adolescents living in a Brazilian urban area is analysed, taking into consideration sociodemographic variables, socioeconomic status and skin colour. Method: This paper presents results from a cross‐sectional study carried out with a random one‐stage cluster sampling of households in the city of Salvador, Bahia, Brazil. The study population comprises 973 individuals from 10 to 21 years of age who answered questionnaires about racial discrimination, socio‐demographic and health‐related variables. Major depression according to DSM‐IV criteria was assessed using a validated Portuguese version of the Patient Health Questionnaire (PHQ). The overall prevalence of major depression was estimated as 10.4%. Results: No statistically significant differences were found for prevalence of major depression or any depressive symptom according to skin colour (Black versus non‐Black). However, adolescents who reported racial discrimination were more likely to have major depression, even after adjustment for age, sex, socioeconomic status, skin colour and self‐esteem (Adjusted Prevalence ratio = 2.00, 95% Confidence Interval: 1.37–2.97). Low self‐esteem was not associated with racial discrimination. Conclusion: Depression among adolescents is a common disorder. Skin colour, a biological component of ethnic differences, was not a factor associated with depression or depressive symptoms. Instead, the perception of racial discrimination was a strong potential risk factor for major depression in this population group, which needs to be addressed in further studies and considered in preventive and mental health care programs.     

Dissecting the Roles of Supervised and Unsupervised Learning in Perceptual Discrimination Judgments

Our ability to compare sensory stimuli is a fundamental cognitive function, which is known to be affected by two biases: choice bias, which reflects a preference for a given response, and contraction bias, which reflects a tendency to perceive stimuli as similar to previous ones. To test whether both reflect supervised processes, we designed feedback protocols aimed to modify them and tested them in human participants. Choice bias was readily modifiable. However, contraction bias was not. To compare these results to those predicted from an optimal supervised process, we studied a noise-matched optimal linear discriminator (Perceptron). In this model, both biases were substantially modified, indicating that the “resilience” of contraction bias to feedback does not maximize performance. These results suggest that perceptual discrimination is a hierarchical, two-stage process. In the first, stimulus statistics are learned and integrated with representations in an unsupervised process that is impenetrable to external feedback. In the second, a binary judgment, learned in a supervised way, is applied to the combined percept.SIGNIFICANCE STATEMENT The seemingly effortless process of inferring physical reality from the sensory input is highly influenced by previous knowledge, leading to perceptual biases. Two common ones are contraction bias (the tendency to perceive stimuli as similar to previous ones) and choice bias (the tendency to prefer a specific response). Combining human psychophysical experiments with computational modeling we show that they reflect two different learning processes. Contraction bias reflects unsupervised learning of stimuli statistics, whereas choice bias results from supervised or reinforcement learning. This dissociation reveals a hierarchical, two-stage process. The first, where stimuli statistics are learned and integrated with representations, is unsupervised. The second, where a binary judgment is applied to the combined percept, is learned in a supervised way.     

Discrimination,arrest history,and major depressive disorder in the U.S. Black population

Everyday discrimination contributes negatively to depressive symptomatology among Blacks in the US and being arrested could add to this depression. Using data from the National Survey on American Life, the present study determined the association between an arrest history and major depressive disorder (MDD), while accounting for discrimination among African Americans, US-born Afro-Caribbeans and first-generation Black immigrants. Findings from logistic regression analyses adjusted for discrimination suggested an arrest history is associated with 12-month MDD (Adjusted OR=1.47; 95% CI=1.02–2.10) and lifetime MDD (Adjusted OR=1.56 CI=1.17–2.09). Accounting for drug and alcohol dependence attenuated the association between arrest history and 12-month MDD, but not lifetime MDD. The associations between arrest history and both 12-month and lifetime MDD, and discrimination and lifetime MDD varied by ethnic/immigrant group. Specifically, while the association between arrest history and MDD (both 12-month and lifetime) was strongest among US-born Afro-Caribbeans, evidence consistent with the immigrant paradox, the association between discrimination and lifetime MDD was particularly relevant for first-generation Black immigrants, suggesting discrimination may hinder the protection of first-generation status. Mental health prevention and treatment programs should target the stress associated with being arrested and experiencing discrimination among US Blacks.     

Prevalence of Current PTSD Symptoms Among a Sample of Black Individuals Aged 15 to 40 in Canada: The Major Role of Everyday Racial Discrimination,Racial Microaggresions,and Internalized Racism

ObjectiveMost Black individuals in Canada report having experienced racial discrimination. Although previous studies have shown that there is a strong relationship between racial discrimination and posttraumatic stress disorder (PTSD), no studies in Canada have documented this association among Black individuals. The present study documents (1) the prevalence of PTSD among Black individuals using data from the Black Communities Mental Health project and (2) risk factors associated with PTSD, including racial microaggressions, everyday racial discrimination, and internalized racism.MethodA total of 860 participants (75.6% of women) aged 15 to 40 years old (M = 24.96, SD = 6.29) completed questionnaires assessing PTSD, experience of traumatic events, racial microaggressions, everyday racial discrimination, and internalized racism.ResultsFindings showed that 95.1% of participants reported exposure to at least one traumatic event during their lifetime. In total, 67.11% of participants reported probable PTSD with no significant difference between men and women (68.2% and 67.8%, χ² = 0.132, p = 0.72). Participants born in Canada were more likely to experience significant PTSD symptoms, compared to those born abroad (70.92% and 53.14%, χ² = 19.69, p < 0.001). A multivariable linear regression model of PTSD symptoms was computed using sociodemographic variables and exposure to traumatic events as independent variables, which explained 25.9% of the variance. In addition to these variables, a second model included racial microaggressions, everyday racial microaggressions, and internalized racism, which explained 51.8% of the variance. The model showed that traumatic events (b = 0.6; p = 0.02), racial microaggressions (b = 0.5; p < 0.001), everyday discrimination (b = 0.2; p = 0.03) and internalized racism (b = 0.5; p < 0.001) were positively associated with PTSD symptoms.ConclusionsThis article highlights the detrimental consequences of racial discrimination against Black people in Canada. Prevention and mental health programs aimed at mitigating its consequences on the lives of Black people and other racialized populations must be implemented.     

A PET Study of Somatosensory Discrimination in Man. Microgeometry Versus Macrogeometry

The regional cerebral blood flow (rCBF) was measured with ¹⁵O-butanol and positron emission tomography (PET) in 10 healthy subjects in order to compare cerebral activation involved in the somatosensory discrimination of microgeometric features with cerebral activation associated with the discrimination of macrogeometric features. Subjects performed two-alternative forced choice (2-AFC) discriminations of pairs of stimuli from a series of quantified standardized stimuli that differed in roughness (microgeometry), and a separate 2-AFC task of smooth tactile stimuli that differed in length (macrogeometry). Results are presented from three conditions: (1) a roughness discrimination task; (2) a length discrimination task; and (3) a control trial in which subjects were required to reproduce similar exploratory finger movements only, but without a specific stimulus to feel. Mean subtraction images were computed using the computerized adjustable brain atlas of Greitz et al. (1991, J. Comput. Assisted Tomogr., 15, 26–38) and areas of significant blood flow change were identified. Both the roughness and the length discrimination tasks activated overlapping cortical fields contralaterally in the anterior and posterior lip of the postcentral sulcus. However, in the length discrimination, activation of the posterior lip of the postcentral sulcus extended deeper into the sulcus and there was also a separate additional area of activation in the anterior part of the precentral gyrus. Furthermore, the length discrimination task activated fields in the overt part of the supramarginal gyrus bilaterally as well as fields in the angular gyrus bilaterally. Thus roughness discrimination uses only a subset of the cortical regions that are needed for the recovery of length information, which requires more extensive somatosensory processing. This finding may be partly explained in that length perception needs both edge detection of the stimuli used, as well as integrated information of surface length and velocity, which is not necessary for roughness perception. Specific differences in the acquisition of necessary tactile information between the two discrimination tasks was reflected in different sampling strategies.