Prefrontal Hemodynamic Response by LMS Cone Activation During Binocular Color Rivalry: An fNIRS Study

Sleep deprivation has been shown to have an antidepressant benefit in a subgroup of depressed patients. Functional imaging studies by the authors and others have suggested that patients with elevated metabolic rates in the anterior cingulate gyrus at baseline are more likely to respond to either sleep deprivation or antidepressant medications than patients with normal metabolic rates. The authors extend their earlier work in a larger group of patients and explore additional brain areas with statistical probability mapping. Thirty-six patients with unipolar depression and 26 normal volunteers were studied with positron emission tomography before and after sleep deprivation. Response to sleep deprivation was defined as a 40% or larger decrease in total scores on the Hamilton Depression Rating Scale. One-third of the depressed patients had a significant response to sleep deprivation. Responders had higher relative metabolic rates in the medial prefrontal cortex, ventral anterior cingulate, and posterior subcallosal gyrus at baseline than depressed patients who did not respond to sleep deprivation and normal volunteers. Lower Hamilton depression scores correlated significantly with lower metabolic rates in the left medial prefrontal cortex. After sleep deprivation, significant decreases in metabolic rates occurred in the medial prefrontal cortex and frontal pole in the patients who responded positively to sleep deprivation. High pretreatment metabolic rates and decreases in metabolic rates after treatment in the medial prefrontal cortex may characterize a subgroup of depressed patients who improve following sleep deprivation and, perhaps, other antidepressant treatments.

1. Data from a series of positron emission tomography (PET) experiments were analyzed with two goals. The first goal was to determine whether there were reliable differences in prefrontal cortex activation across two different speech production tasks. Such differences are important in determining functional subdivisions within prefrontal cortex. The second goal was to determine whether there were any gender differences across the two speech production tasks. 2. To accomplish these goals, PET subtraction images were generated for each of two speech production tasks (stem completion and verb generation). For the stem completion task, subjects viewed word stems (e.g., "GRE") and said aloud words that could complete the stems (e.g., "green"). For the verb generation task, subjects viewed nouns (e.g., "CHAIR") and said aloud words that were meaningfully related verbs (e.g., "sit"). Different groups of subjects performed the stem completion (N = 29) and verb generation (N = 32) tasks. 3. Data from each task subtraction were further divided by gender group (i.e., verb generation: male group; verb generation: female group, etc.). PET activations were separately identified in prefrontal cortex for each of the four resulting images. Activations were identified primarily in left prefrontal cortex for both tasks and both gender groups. Activations in right prefrontal cortex were small or absent. 4. Across tasks, the subtraction images showed both common activations in prefrontal cortex and one clear difference. Activations in left inferior prefrontal cortex (near Brodmann's areas 44 or 45) were observed in both male and female group images for both task subtractions. Activations in left anterior prefrontal cortex (near Brodmann's areas 10 or 46) were only observed for the verb generation subtraction images, formally demonstrating a functional dissociation between left inferior prefrontal cortex and more anterior prefrontal cortex. 5. This dissociation between prefrontal areas was highly robust and reliable across both gender groups. The left inferior prefrontal area(s) common to all of the subtraction images appears to be activated by tasks that demand high-level word retrieval and production processes. This area is distinct from the more anterior area(s), which is not always activated by such tasks. Dissociations in prefrontal areas are important because current descriptions of human functional anatomy often treat activations within large regions of cortex (e.g., dorsolateral prefrontal cortex) as single entities. 6. No qualitative differences in activation between gender groups were detected. For both subtractions, all activations identified within one gender group generalized to the other gender group. For the verb generation subtraction image, however, activations in male subjects were larger in magnitude than in female subjects.

Association between social functioning and prefrontal hemodynamic responses in elderly adults

Prefrontal cortical unit activity and delayed alternation performance in monkeys.

ObjectiveColor and spatial location are key cues influencing visual selection in binocular color rivalry, jointly modulating attentional resource allocation and prefrontal cortex (PFC) activity. However, how these cues—individually and in combination—regulate ocular behavior and PFC activation remains insufficiently understood and lacks systematic empirical investigation.MethodsThis study integrates eye tracking, functional near-infrared spectroscopy (fNIRS), and reaction time measurements to systematically investigate the cortical and oculomotor response characteristics under a binocular rivalry paradigm, focusing on color rivalry (Color stimuli), spatial location (Location stimuli), and their combined (Color & Location stimuli).ResultsThe results revealed that Color stimuli elicited rapid saccades, significant pupil dilation, and a decrease in prefrontal HbO concentration. Location stimuli induced stable saccadic patterns and a typical biphasic HbR response in BA46. The combined Color & Location stimuli triggered significant changes in oculomotor behavior during the later processing stage, accompanied by a marked increase in HbO activation in BA10, suggesting its dominant role in multisensory integration and cognitive resource reallocation. Further coupling analyses showed a significant positive correlation between prefrontal HbO concentration and reaction time (r = 0.555, p < 0.01), and a significant negative correlation between HbO concentration and saccade amplitude (r = –0.376, p < 0.05), consistent with the theoretical predictions of the “neural efficiency–cognitive load trade-off” model. Task-dependent coupling relationship were also observed among oculomotor parameters and between eye movement and cerebral hemodynamic signals.ConclusionColor stimuli induce rapid saccadic behavior and impose higher prefrontal load, Location stimuli engage a more efficient dorsal pathway, while Color & Location stimuli intensify resource rivalry and induce a processing bottleneck, manifested as prolonged reaction times co-occurring with heightened cortical activation.

Color vision deficiency in retinitis pigmentosa

The neural response of the prefrontal cortex varies with the color difference in binocular rivalry: Evidence from fNIRS.

Chromatic sensitivity was assessed in patients with pregeniculate and postgeniculate lesions. We examine changes in central vision along at foveal fixation and in each of the four paracentral quadrants of the visual field using the Colour Assessment and Diagnosis (CAD) test, a dynamic luminance contrast masking technique that isolates the use of Red / Green (RG) and Yellow / Blue (YB) colour signals. Because the extraction of colour signals in early visual processing involves opponent mechanisms, subjects with congenital RG loss of sensitivity exhibit symmetric increase in thresholds towards the long wavelength (“red”) and middle wavelength (“green”) regions of the spectrum locus. This is also frequently the case with acquired loss of chromatic sensitivity as a result of retinal or optic nerve disease. The findings from this study represent an exception to this rule. The patients investigated showed a marked asymmetry in colour thresholds. The study reveals how discrete, localized damage to visual pathways can cause selective loss of visual function and how the latter varies with retinal topography.The 36 pregeniculate patients investigated exhibited impairment in both RG and YB. Loss of colour vision was symmetrical for both RG and YB discrimination. Some pregeniculate patients exhibited substantial loss of colour vision in areas where perimetric loss was largely absent. All quadrants revealed similar symmetric loss of colour sensitivity.In 23 patients with postgeniculate lesions, patients with pre‐striate damage exhibited symmetric loss of chromatic sensitivity which affected either one or both chromatic mechanisms. Striate or extra‐striate lesions tended to exhibit general loss of colour vision within the area identified by visual field testing. More specific chromatic loss was associated with less impaired areas that were often normal on perimetric testing. Some patients with striate or extra‐striate lesions presented with asymmetric chromatic loss for one or more colour categories. When striate or extra‐striate lesions were also accompanied by underlying pre‐striate damage, chromatic sensitivity loss was always symmetric.The findings from this study show that the loss of chromatic sensitivity in cerebral achromatopsia depends strongly on the exact location and extent of the lesion with significant variation over the visual field. The same subject can exhibit loss of chromatic sensitivity that is either RG or YB specific, but also, spatially localized, non‐opponent loss of sensitivity for primary colours.

EPA-1047 – Short-term effects of antipsychotic treatment on prefrontal hemodynamic responses in first-episode schizophrenia during tower of london: A multi-channel nirs study

We investigated prefrontal cortex (PFC) hemodynamic response, through functional near infrared spectroscopy (fNIRS) during executive function (EF) processing in response to acute high intensity intermittent exercise (HIIE) in young adults. We also assessed the associated sex differences in the cognitive scores and related PFC hemodynamic functions in response to HIIE. 49 young healthy adult participants (32 women, 17 men) were randomly assigned to either control or HIIE intervention groups. HIIE group participants performed 4 × 4 minutes of HIIE on cycle ergometer with 3 minutes of active recovery between the bouts; control group relaxed for the time equivalent to intervention. fNIRS data was collected during the performance of the EF tests including Color Word Stroop Test (CWST) and Trail Making Test (TMT) in pre and post sessions in both the groups. Results indicated a significant change in the hemodynamic response in the form of increased oxygenated and decreased deoxygenated hemoglobin in the PFC areas specific to the EF tasks, with improved CWST and TMT scores in response to HIIE intervention. PFC activation was different in men and women in response to HIIE, however similar scores of task performance were observed in men and women during the performance of executive functions in response to HIIE. The study concludes that an acute HIIE session improves executive function which is associated with an increase activation of PFC. Sex differences exist in the activation of PFC in response to HIIE during EF processing. Our study adds to the current evidence regarding exercise and cognition.

Activity in the Lateral Prefrontal Cortex Reflects Multiple Steps of Future Events in Action Plans

Learning Substrates in the Primate Prefrontal Cortex and Striatum: Sustained Activity Related to Successful Actions

Abnormalities in rod and cone photoreceptor morphology have been reported in normal aging retinas in the absence of known pathology and have been taken as an indicator of susceptibility to retinal disease. Some loss of visual performance may therefore precede retinal structural changes that can be detected reliably using conventional fundus imaging techniques. Red/green (RG) and yellow/blue (YB) colour discrimination thresholds are sensitive measures of normal retinal function and poor YB discrimination is often taken as an indicator of retinal disease, though it is generally acknowledged that RG loss is also present in most cases of acquired deficiency. Although structural changes in age-related macular degeneration (AMD) and diabetes share some similarities, significant differences remain and this may result in different patterns of RG and YB loss. The aim of this study was to quantify and compare the severity of RG and YB loss of chromatic sensitivity in patients with AMD and diabetes. Patients with varying severity of AMD and diabetes and normal subjects of similar age were recruited for the study. RG and YB colour detection thresholds were measured in the two groups of patients and the control group, using the Colour Assessment and Diagnosis (CAD) test. Each AMD subject investigated showed significant, but unequal loss of YB and RG chromatic sensitivity, with YB discrimination showing the greatest loss. Diabetic subjects also exhibited reduced chromatic sensitivity, but with almost equal and highly correlated RG and YB thresholds (R(2) = 0.99). The severity of colour vision loss measured with the CAD test also correlates well with a clinical classification index of disease progression in AMD, and with the level of hyperglycaemic control in diabetes. These findings suggest that accurate measurements of RG and YB colour thresholds can provide a sensitive measure of functional change in diseases of the retina with patterns of loss that differ significantly in AMD and diabetes.

In psychotic patients, altered hemodynamic responses and their significance in differential diagnosis are reported. However, the effects of antipsychotics and the associated increase of prolactin levels on prefrontal hemodynamic responses are not well understood. Antipsychotics may affect neurovascular coupling directly by inhibiting dopamine receptors1 or indirectly by increasing prolactin, which induces regional vasoconstriction.2 In a single-center observational study, we investigated the relation between prolactin levels and prefrontal hemodynamic responses. A total of 86 psychiatric patients, including 69 treated with antipsychotics, underwent near-infrared spectroscopy (NIRS) by a 22-channel topography system for diagnosis of psychotic disorders. We measured serum prolactin levels within a week from NIRS examination (Table S1). Changes of the concentration of oxygenated hemoglobin in prefrontal cortices were evaluated during a verbal fluency test, and three NIRS indices (integral value: size of area during the activation, centroid value: centroid time of area throughout, and initial value: axis assessed by an initial change) were analyzed against prolactin levels and chlorpromazine-equivalent doses by sex and cortex region. The ethics committee of Kusatsu Hospital approved this study, and informed consent to analyze the stacked data was obtained from all subjects. Serum prolactin levels were significantly negatively correlated with integral values and initial values at frontal and temporal regions in male subjects (Fig. S1), whereas, no such correlations were found in female subjects or between the chlorpromazine-equivalent doses and NIRS indices (Table S2). These results indicated that a higher prolactin level caused a decline in prefrontal hemodynamic responses in male subjects. The brain consumes high energy and requires adequate blood flow, which is facilitated by a tight coupling between neuronal activity and regional cerebral blood flow. Such neurovascular coupling is maintained by numerous mediators, such as nitric oxide, ion channels, and astrocytes.3 The prolactin receptor is expressed on astrocytes, which control various clinically relevant functions.4 Thus, activation of the prolactin receptor initiates multiple second-messenger cascades, which influence the vascular tone during tasks.4 Moreover, sex differences seemed to exist regarding the prolactin regulation on vascular tonus. Although dependent variables, such as psychiatric conditions and treatment durations, were not considered, our findings may suggest that prolactin levels relate to prefrontal hemodynamic responses in a psychiatric setting. Prolactin controls a vast number of physiological functions in the nervous system; however, its hemodynamic effect remains unclear. Further research to elucidate the effect of prolactin on cerebral blood flow via astrocyte prolactin receptor is needed. The authors declare no conflicts of interest. Please note: The publisher is not responsible for the content or functionality of any supporting information supplied by the authors. Any queries (other than missing content) should be directed to the corresponding author for the article.

Despite years of research into bipolar disorder (manic depression), its underlying pathophysiology remains elusive. It is widely acknowledged that the disorder is strongly heritable, but the genetics are complex with less than full concordance in monozygotic twins and at least four susceptibility loci identified. We propose that bipolar disorder is the result of a genetic propensity for slow interhemispheric switching mechanisms that become 'stuck' in one or the other state. Because slow switches are also 'sticky' when compared with fast switches, the clinical manifestations of bipolar disorder may be explained by hemispheric activation being 'stuck' on the left (mania) or on the right (depression). Support for this 'sticky' interhemispheric switching hypothesis stems from our recent observation that the rate of perceptual alternation in binocular rivalry is slow in euthymic subjects with bipolar disorder (n = 18, median = 0.27 Hz) compared with normal controls (n = 49, median = 0.60 Hz, p < 0.0005). We have presented evidence elsewhere that binocular rivalry is itself an interhemispheric switching phenomenon. The rivalry alternation rate (putative interhemispheric switch rate) is robust in a given individual, with a test-retest correlation of more than 0.8, making it suitable for genetic studies. The interhemispheric switch rate may provide a trait-dependent biological marker for bipolar disorder.