Sex differences of cognitive load effects on object-location binding memory

In this study, we investigated where the sex differences of object-location binding memory performance were influenced by the cognitive load. We used the fractal objects version of the ‘What was where?’ task to measure object memory, location memory and objection-location binding memory. Cognitive load was controlled by task difficulty presented two sessions: one session randomly displayed three or four fractal objects (Session 34) and the other session four or five objects (Session 45). The results showed that females outperformed males on object-location binding memory. Interestingly, even when the four object trials were compared between Session 34 and Session 45, in which we believed that the level of difficulty was similar while cognitive load varied, the swap error of males was significantly increased in Session 45 compared to females. In conclusion, there may be sex differences in object-location binding memory and the males could be more sensitive about the cognitive load than females.

A Trainable Hearing Aid Algorithm Reflecting Individual Preferences for Degree of Noise-Suppression, Input Sound Level, and Listening Situation

OBJECTIVES: In an effort to improve hearing aid users’ satisfaction, recent studies on trainable hearing aids have attempted to implement one or two environmental factors into training. However, it would be more beneficial to train the device based on the owner’s personal preferences in a more expanded environmental acoustic conditions. Our study aimed at developing a trainable hearing aid algorithm that can reflect the user’s individual preferences in a more extensive environmental acoustic conditions (ambient sound level, listening situation, and degree of noise suppression) and evaluated the perceptual benefit of the proposed algorithm. METHODS: Ten normal hearing subjects participated in this study. Each subjects trained the algorithm to their personal preference and the trained data was used to record test sounds in three different settings to be utilized to evaluate the perceptual benefit of the proposed algorithm by performing the Comparison Mean Opinion Score test. RESULTS: Statistical analysis revealed that of the 10 subjects, four showed significant differences in amplification constant settings between the noise-only and speech-in-noise situation (P<0.05) and one subject also showed significant difference between the speech-only and speech-in-noise situation (P<0.05). Additionally, every subject preferred different β settings for beamforming in all different input sound levels. CONCLUSION: The positive findings from this study suggested that the proposed algorithm has potential to improve hearing aid users’ personal satisfaction under various ambient situations.

Decoding Saccadic Directions Using Epidural ECoG in Non-Human Primates

A brain-computer interface (BCI) can be used to restore some communication as an alternative interface for patients suffering from locked-in syndrome. However, most BCI systems are based on SSVEP, P300, or motor imagery, and a diversity of BCI protocols would be needed for various types of patients. In this paper, we trained the choice saccade (CS) task in 2 non-human primate monkeys and recorded the brain signal using an epidural electrocorticogram (eECoG) to predict eye movement direction. We successfully predicted the direction of the upcoming eye movement using a support vector machine (SVM) with the brain signals after the directional cue onset and before the saccade execution. The mean accuracies were 80% for 2 directions and 43% for 4 directions. We also quantified the spatial-spectro-temporal contribution ratio using SVM recursive feature elimination (RFE). The channels over the frontal eye field (FEF), supplementary eye field (SEF), and superior parietal lobule (SPL) area were dominantly used for classification. The α-band in the spectral domain and the time bins just after the directional cue onset and just before the saccadic execution were mainly useful for prediction. A saccade based BCI paradigm can be projected in the 2D space, and will hopefully provide an intuitive and convenient communication platform for users.

Effects of the Simultaneous Application of Nonlinear Frequency Compression and Dichotic Hearing on the Speech Recognition of Severely Hearing-Impaired Subjects: Simulation Test

OBJECTIVES: The clinical effects of the simultaneous application of nonlinear frequency compression and dichotic hearing on people with hearing impairments have not been evaluated previously. In this study, the clinical effects of the simultaneous application of these two techniques on the recognition of consonant-vowel-consonant (CVC) words with fricatives were evaluated using normal-hearing subjects and a hearing loss simulator operated in the severe hearing loss setting. METHODS: A total of 21 normal-hearing volunteers whose native language was English were recruited for this study, and two different hearing loss simulators, which were configured for severe hearing loss in the high-frequency range, were utilized. The subjects heard 82 English CVC words, and the word recognition score and response time were measured. RESULTS: The experimental results demonstrated that the simultaneous application of these two techniques showed almost even performance compared to the sole application of nonlinear frequency compression in a severe hearing loss setting. CONCLUSION: Though it is generally accepted that dichotic hearing can decrease the spectral masking thresholds of an hearing-impaired person, simultaneous application of the nonlinear frequency compression and dichotic hearing techniques did not significantly improve the recognition of words with fricatives compared to the sole application of nonlinear frequency compression in a severe hearing loss setting.

The Current Status of Evaluation Technologies for the Function of Human Olfaction / 한양의대학술지

The sense of smell is one of the essential tools for all living things to survive. With recent increase in diseases associated with olfactory dysfunction, the evaluation of olfactory function aims to shed light on the understanding and assessment of the human olfactory system. The methods for assessing the olfactory function are largely divided into electrophysiological and psychophysical methods. The psychophysical inspections such as University of Pennsylvania Smell Identification Test (UPSIT), The Sniffin' Stick, and T & T Olfactometer are methods mostly based on questionnaires or simple apparatus. Those have been generally used in clinical and research field due to their relatively short examination time and low cost. The electrophysiological tests evaluate olfactory function based on objective measurements like biosignals and medical imaging. Compared to the psychophysical methods, they comparably have higher reliability and are possible to assess more specific diagnosis. However, the system configuration seems to be more complicated. In this paper, we review the overall evaluation methods of olfactory functions and suggest complementary points to improve conventional technologies.

Depressive Symptoms and Brain Metabolite Alterations in Subjects at Ultra-high Risk for Psychosis: A Preliminary Study

OBJECTIVE: Recent neuroimaging studies have suggested that brain changes occur in subjects at ultra-high risk (UHR) for psychosis while experiencing prodromal symptoms, among which depression may increase the risk of developing a psychotic disorder. The goal of this study is to examine brain metabolite levels in the anterior cingulate cortex, the left dorsolateral prefrontal cortex and the left thalamus in subjects at UHR for psychosis and to compare brain metabolite levels between the UHR subjects with comorbid major depressive disorder and healthy controls. METHODS: Proton magnetic resonance spectroscopy was used to examine brain metabolite levels. Twenty UHR subjects and 20 age- and intelligence quotient (IQ)-matched healthy controls were included in this study. RESULTS: Overall, no significant differences were observed in any metabolite between the UHR and healthy control group. However, UHR subjects with major depressive disorder showed significantly higher myo-inositol (Ins) levels in the left thalamus, compared to the healthy control. CONCLUSION: Our results demonstrate that increased thalamic Ins level is associated with prodromal depressive symptoms. Further longitudinal follow-up studies with larger UHR sample sizes are required to investigate the function of Ins concentrations as a biomarker of vulnerability to psychosis.

Depressive Symptoms and Brain Metabolite Alterations in Subjects at Ultra-high Risk for Psychosis: A Preliminary Study

OBJECTIVE: Recent neuroimaging studies have suggested that brain changes occur in subjects at ultra-high risk (UHR) for psychosis while experiencing prodromal symptoms, among which depression may increase the risk of developing a psychotic disorder. The goal of this study is to examine brain metabolite levels in the anterior cingulate cortex, the left dorsolateral prefrontal cortex and the left thalamus in subjects at UHR for psychosis and to compare brain metabolite levels between the UHR subjects with comorbid major depressive disorder and healthy controls. METHODS: Proton magnetic resonance spectroscopy was used to examine brain metabolite levels. Twenty UHR subjects and 20 age- and intelligence quotient (IQ)-matched healthy controls were included in this study. RESULTS: Overall, no significant differences were observed in any metabolite between the UHR and healthy control group. However, UHR subjects with major depressive disorder showed significantly higher myo-inositol (Ins) levels in the left thalamus, compared to the healthy control. CONCLUSION: Our results demonstrate that increased thalamic Ins level is associated with prodromal depressive symptoms. Further longitudinal follow-up studies with larger UHR sample sizes are required to investigate the function of Ins concentrations as a biomarker of vulnerability to psychosis.

Canine model of ischemic stroke with permanent middle cerebral artery occlusion: clinical and histopathological findings

The aim of the present study was to assess the clinical and histopathological findings in a canine model of ischemic stroke. Cerebral ischemic stroke was induced by middle cerebral artery occlusion in four healthy beagle dogs using silicone plugs. They showed neurological signs of forebrain dysfunction such as reduced responsiveness, head turning, circling, postural reaction deficits, perceptual deficits, and hemianopsia. These signs gradually regressed within 4 weeks without therapy. On magnetic resonance imaging, T2 hyperintensity and T1 hypointensity were found in the cerebral cortex and basal ganglia. These lesions were well-defined and sharply demarcated from adjacent brain parenchyma with a homogenous appearance. No abnormalities of the cerebrospinal fluid were observed. At necropsy, atrophic and necrotic lesions were observed in the cerebral cortex. The cerebral cortex, basal ganglia, and thalamus were partially unstained with triphenyl-tetrazolium chloride. Histopathologically, typical features of infarction were identified in cortical and thalamic lesions. This study demonstrates that our canine model resembles the conditions of real stroke patients.

Effects of Mirtazapine on Hippocampal Metabolites of Female Patients with Major Depression / 대한정신약물학회지

OBJECTIVE: Recent studies suggested that the neurotrophic effects might be a major therapeutic mechanism of antidepressants. However, these effects have not been confirmed yet in depressed patients. We investigated whether mirtazapine treatment has the neurotrophic effects in depressed patient by using (1)H-MRS and explored the relationship between these effects and clinical improvements and neuropsychological functions. METHODS: Fourteen female, right-handed patients with major depressive disorder and 12 healthy controls participated in the study. Before the treatment with mirtazapine, we measured severity of illness, neuropsychological functions, and the levels of NAA, Cho and Cr in both hippocampi using (1)H-MRS in the depressed subjects. After the treatment with mirtazapine for 6 weeks, we repeated the measures of the pretreatment condition in the depressed subjects. We also measured variables of severity of illness and hippocampal metabolites with (1)H-MRS in the control group. RESULTS: There were no significant differences in NAA/Cr, Cho/Cr, and Cho/NAA between the depressed subjects and the control group. However, after the treatment with mirtazapine, there were significant improvements in severity of illness, immediate memory, and delayed memory. The posttreatment ratio of the total hippocampal Cho/Cr was significantly lowered than the ratio of the pretreatment Cho/Cr. However, the percent changes of the hippocampal Cho/Cr from the pretreatment Cho/Cr ratio were not correlated with the changes of severity of illness or neuropsychological functions from the pretreatment condition. CONCLUSIONS: These findings indicate that mirtazapine may reduce the level of choline metabolites by stabilizing the effect on the cholinergic neurons, reducing turnover or metabolism of neuronal membranes, or modulating the neuroendocrine systems in the depressed patients. However, this effect is not necessarily related to clinical improvements. Further studies on the therapeutic action of mirtazapine are needed.

1H-MRS Study on the Frontal Lobe White Matter Metabolites in Female Patients with Depression: Relations to Impulsivity / 대한정신약물학회지

OBJECTIVE: The frontal lobe white matter (FLWM) is suggested to play an important role in the pathophysiology of depression. In this study, metabolites in the normal appearing FLWM and their clinical meaning in female subjects were evaluated. METHODS: Using proton-magnetic resonance spectroscopy, the ratios of metabolite peaks in the FLWM were measured in vivo in 14 female patients with major depressive disorder and were compared with 12 age-matched normal controls. The ratios' clinical significance was analyzed with respect to severity of depression (Hamilton Depression rating Scale score and Beck Depression Inventory score) and trait of impulsivity (Barratt Impulsiveness Scale). RESULTS: There were no significant differences in the NAA/Cr, Cho/Cr, Cho/NAA ratio between depressed and control subjects. But right FLWM Cho/Cr ratios in control and depressed subjects were found to be positively correlated with total and motor impulsiveness score as measured by the Barratt Impulsiveness Scale. CONCLUSION: The biochemical changes in the FLWM may provide some of the neurobiological substrates to personality trait, impulsivity. Further researches on the underlying mechanisms of impulsivity traits are needed.

The Clinical Meanings of the Hippocampal Metabolites of Female Patients with Major Depressive Disorder / 대한정신약물학회지

OBJECTIVE: Stress and elevated levels of glucocorticoids in patients with major depressive disorder (MDD) have been hypothesized to be associated with damage to the hippocampus. However the relationship between depression and hippocampal structure is unconfirmed. We investigated whether the chemical changes will occurr in the hippocampus of patients with MDD by using 1H-magnetic resonance spectroscopy (MRS) and explored the clinical meanings of hippocampal metabolites. METHODS: Fourteen female, right-handed patients with major depressive disorder and 12 healthy controls (age, sex, education and their dextrality matched) were included. We measured variables of time course of illness, severity of illness, levels of NAA, Cho and Cr in both hippocampus using 1HMRS. In addition, we performed neuropsychological tests in depressed subjects. RESULTS: There were no significant difference in the NAA/Cr, Cho/Cr, Cho/NAA between depressed and control subjects. In depressed subjects, significant negative correlations were observed between hippocampal NAA/Cr and duration of illness, duration of unmedication, severity of illness, respectively. Right hippocampal NAA/Cr was correlated with RCFT scores. CONCLUSION: These findings indicate damage to the hippocampus may not be a common feature in all depressed patients. However the results suggest that the illness burden and past treatment may influence hippocampal neurons and neuronal network in patients with MDD. Also, chemical changes in hippocampus may be associated with severity of illness and memory function.

Correlates of N-acetylaspartate and Cognitive Dysfunctions in Drug-naive Patients with Obsessive-compulsive Disorder: A Proton MRSI Study / 신경정신의학

OBJECTIVES: Reductions of N-acetylaspartate (NAA), a putative marker of neuronal viability, within the subcortical structures in patients with obsessive-compulsive disorder (OCD) are well documented. However, there has been no report of the NAA level in cortical structures. The authors used proton magnetic resonance spectroscopic imaging (1H-MRSI) to assess potential reductions of NAA in the frontal white matter, prefrontal gray matter, parietal gray and white matter, and the cingulate in drugnaive patients with OCD and explored the relationship between the brain metabolites and the degree to the dysfunction on the neuropsychological performances. METHODS : Thirteen drug-naive patients who met DSM-IV criteria for OCD and 13 healthy age-, sex-, handness- matched control subjects were studied. Subjects underwent MRI and 1H-MRSI and the peaks of NAA, creatine+phosphocreatine (Cr), and choline-containing compounds (Cho) were measured. Differences between patients and control subjects were tested for each metabolite ratio, and the relations between metabolite ratios and clinical symptoms, neuropsychological performances were examined. RESULTS : Upon comparison with normal controls, NAA/Cr ratio was significantly reduced in patients for the prefrontal gray matter, frontal white matter and anterior cingulate. There was no difference in Cho/Cr or NAA/Cho in any region. Also, a significant positive correlation was found between prefrontal NAA/Cr ratio and the delayed recall score of the Rey-Osterrieth Complex Figure Test in patients with OCD. CONCLUSION : The reduced NAA/Cr ratio in the prefrontal gray matter and frontal white matter suggests that OCD patients have lower neuronal viability than normal comparisons and it may be related to impaired organizational strategies in patients with OCD. These results support a role for the frontal-subcortical circuitry in a neurobiologic model of OCD.

Development and Clinical Trial of Driving Simulator with Virtual Reality

OBJECTIVE: To evaluate safely the driving ability of the handicapped with developed driving simulator in the virtual environment and to investigate clinical usefulness. METHOD: A real car was remodeled for realism and equipped it with hand control device for driving of the handicapped. The subjects were 10 normal people with driving license and 15 patients with thoracic or lumbar spinal cord injury who had driving experience. 5 driving skills were measured (average speed, steering stability, centerline violation, traffic signal violation, and time taken in driving) in various road conditions. The normal participants manipulated the gas pedal and the brake by their foot while the patients did with their hands. After they finished to drive the whole course, they answered the questions ("How realistic the driving simulator seems to you" and "How much your fear reduced") RESULTS: 1) Four driving skills measured between two groups (normal vs. handicapped) were not significantly different (p>0.05). 2) In 4 kinds (start road, speed limit road, sharp curve road and left turn) of the road conditions, the average speed of the patients group was significantly different from the normal group (p<0.05). 3) Eleven patients (73%) reported that their driving fear was reduced and the score of "how realistic" question was 51.5% in average. CONCLUSION: This developed driving simulator will be able to be used for one of the programs for evaluating and training the driving skill of the handicapped and need to enhance the reality of driving simulator.