Evaluating the effects of functional orthodontic treatment on mandibular osseous structure using fractal dimension analysis of dental panoramic radiographs.

OBJECTIVE: To evaluate the effects of functional appliance treatment on mandibular trabecular structure using fractal dimension (FD) analysis of dental panoramic radiographs. MATERIALS AND METHODS: This study was conducted using digital panoramic radiographs of 45 patients with Class II malocclusion treated with functional appliances (treatment group, mean age: 11.39 ± 0.97 years; 23 girls, 22 boys) acquired before (T0) and after (T1) treatment and the panoramic radiographs of 45 control subjects who had undergone no orthodontic treatment (control group, mean age: 11.31 ± 0.87 years; 23 girls, 22 boys). FD values in the condylar process, mandibular corpus, and mandibular angle were analyzed from the panoramic radiographs of both groups. RESULTS: Analysis of changes in FD between T0 and T1 revealed significant increases in the FD values of the right and left condylar processes and right mandibular corpus in the treatment group (P < .001) and in the right condylar process in the control group (P < .05). Between-group comparisons demonstrated that the treatment group showed greater changes in the condylar process (right, P < .001; left, P < .05) and right mandibular corpus (P < .05) compared to controls. Correlation analysis between the cephalometric and FD changes in the treatment group showed the right condylar process changes were negatively correlated with GoGn/SN angle (P < .05) and positively correlated with Co-Go (P < .05), although these correlations were weak. CONCLUSIONS: FD analysis demonstrated significant changes in trabeculation of the condyle and mandibular corpus in the treatment group compared to the control group. Functional appliance treatment may lead to skeletal correction by altering skeletal form and trabeculation of the mandibular bone.

Contrast-to-noise ratios of different dental restorative materials: an in-vitro cone beam computed tomography study.

PURPOSE: In radiological views, strong beam hardening and streaking artifacts occur due to high-density structures and polyenergetic X-ray beams, and these lead to misdiagnosis. This study was performed in vitro to compare the contrast-to-noise ratio (CNR) of commonly used dental restorative materials by using Cone Beam Computed Tomography (CBCT) images with and without artifact reduction (AR) mode. MATERIALS AND METHODS: A total of 108 molar teeth were restored with nine different groups of restorative materials, with each group containing 12 teeth. Teeth were placed in a dry human mandible and scanned, one by one, via Planmeca 3D ProMax (Planmeca, Helsinki, Finland) with and without AR mode. Images were analyzed using ImageJ software (National Institutes of Health, Bethesda, MD) to calculate the CNR. RESULTS: CNR was calculated to be the highest in compomer (Glassiosite) images without AR mode (mean: 3.36) and with AR mode (mean: 3.61). CNR was calculated to be the lowest in amalgam (Tytin) images without AR mode (mean: 0.21) and with AR mode (mean: 0.23). A significant difference was found between materials in terms of CNR measurements (p ≤ 0.05). CNR measurements were increased after the AR mode application (p ≤ 0.05). CONCLUSION: AR mode was effective in reducing artifacts arising from dental materials on CBCT images, so it is necessary to use AR mode for correct diagnoses.

Assessment of Maxillary Sinus Changes After Le Fort I Osteotomy Surgery.

OBJECTIVE: The goal of this retrospective study is to examine the changes of maxillary sinus volume, sinus membrane thickness (SMT) and the distance between the floor of maxillary sinus and ostium after Le Fort I osteotomy. METHODS: A total of 30 patients who underwent Le Fort I osteotomy were evaluated just before and 1 year after the surgical operation. Linear and volumetric measurements were done via 3D-DOCTOR software on sectional and 3D images. RESULTS: Decrease in maxillary sinus volume, increase in SMT and no change in distance between the floor of the maxillary sinus and ostium were detected after surgery. After surgery, SMT was found higher in advancement + impaction group. CONCLUSION: This paper clarified that Le Fort I osteotomy affects the volume and thickness of the maxillary sinuses that may lead to deterioration of the ciliary activity and failure in the drainage which are predisposing factors for sinus pathologies. In maxillary osteotomies of later ages, maxillary sinus examination and follow-up should be performed regularly in order to maintain sinus health.

Evaluation of a metal artifact reduction algorithm and an optimization filter in the estimation of peri-implant dehiscence defects by using cone beam computed tomography: an in-vitro study.

OBJECTIVES: The aim of this study was to assess the effect of a metal artifact reduction (MAR) algorithm and the adaptive image noise optimizer (AINO) optimization filter in the detection of peri-implant dehiscences with cone beam computed tomography (CBCT). STUDY DESIGN: Nine implants (3 zirconium, 3 titanium, and 3 zirconium-titanium) were placed in 3 sheep heads. Dehiscences were created on the buccal and lingual/palatal surfaces. A total of 9 defects and 9 controls with no defects were evaluated by 3 observers. Each sheep head was scanned 5 times with 4 scan modes; (1) without MAR/without AINO; (2) with MAR/without AINO; (3) without MAR/with AINO; and (4) with MAR/with AINO. Receiver operating characteristic analysis and weighted kappa coefficients were used to calculate diagnostic efficacy and intra- and interobserver agreements for each implant type and scan mode. RESULTS: For all implant types, dehiscences were most accurately detected when both MAR and AINO were applied (P ≤ .045). Detection of dehiscences was more accurate with titanium implants (P ≤ .040). There were no significant differences in agreement among and between the observers. CONCLUSIONS: The use of both MAR and AINO enhanced the detection accuracy of artificially created dehiscences in proximity to implants. Their combined use is recommended for detecting peri-implant dehiscences.

Evaluation of osseous changes in dental panoramic radiography of thalassemia patients using mandibular indexes and fractal size analysis.

OBJECTIVE: This study aimed to evaluate the radiomorphometric indexes and fractal dimension (FD) on dental panoramic radiography (DPR) of Thalassemia Major (TM) patients. METHODS: In 59 TM patients and in 59 healthy control subjects, mandibular cortical index (MCI), mandibular cortical width (MCW), panoramic mandibular index (PMI), and FD of four different regions (FD1-4) were evaluated and compared using DPRs. RESULTS: The distribution of MCI in TM patients was similar to control subjects (p > 0.05). The mean MCW was significantly lower in TM patients (p = 0.001). There was no significant difference in PMI between TM patients and control subjects. The mean of FD measured in the supracortical area above the angle of mandible (FD2), in the anterior to the mental foramen (FD4) and mean FD of four different regions was significantly lower in TM patients (p = 0.003, p = 0.001, and p = 0.014, respectively). CONCLUSIONS: The radiomorphometric indices and fractal dimensions evaluated in the panoramic radiograph are capable of identifying thalassemia patients' jaw bone, and the results of DPR scanning can be used to refer these patients to appropriate medical investigation.

Assessment of signal-to-noise ratio and contrast-to-noise ratio in 3 T magnetic resonance imaging in the presence of zirconium, titanium, and titanium-zirconium alloy implants.

OBJECTIVE: We quantitatively compared the signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) in T1 weighted imaging (WI) and T2 WI sequences in 3 Tesla (T) magnetic resonance imaging (MRI) using zirconium, titanium (grades 4 and 5), and titanium-zirconium alloy implants to evaluate the effect of implant type and imaging sequence. STUDY DESIGN: MRI was acquired using a 3 T magnet with a 16-channel head coil. Implants of each type were mounted in gel and scanned in axial, coronal, and sagittal planes using fast spin echo sequences in T1 WI (TR = 600, TE = 12 milliseconds) and T2 WI (TR = 3000, TE = 80 milliseconds) sequences. Data were transferred to Synapse 3-D software, and images were measured twice by an oral and maxillofacial radiologist blinded to the type of implants. RESULTS: Zirconium implants resulted in the lowest SNR and CNR values (P < .05). No significant differences were identified between titanium (grades 4 and 5) and titanium-zirconium implants. The T2 WI sequence had a significantly higher SNR and CNR than T1 WI. There was no difference in intraobserver agreement between T1 WI and T2 WI. CONCLUSIONS: CNR and SNR at 3 T MRI are dependent on implant type and imaging sequence. Titanium (grades 4 and 5) and titanium-zirconium implants and the T2 WI sequence produced higher SNR and CNR values.

Estimation of contrast-to-noise ratio in CT and CBCT images with varying scan settings in presence of different implant materials.

OBJECTIVES: To assess the contrast-to-noise ratio (CNR) of four different types of dental implant materials in CT and cone beam CT (CBCT) images with varying scan settings. METHODS: Four different types of implants: zirconium (Zr), titanium (Ti) Grade 4 and 5 and titanium-zirconium (Ti-ZrO2) alloy were placed in a 3% gelatin phantom in a cylindrical plastic container and scanned with two different CT machines (GE Medical systems and Toshiba Medical Systems) and one CBCT machine (I-CAT, Imaging Sciences International) with different voxel sizes of 0.2, 0.25, 0.3 and 0.4 mm. Images were analyzed using ImageJ software with the purpose of estimating the CNR. RESULTS: The CNR obtained from images acquired with CT was lower than the CBCT with all voxel sizes tested. 0.3 and 0.4 mm voxel sizes exhibited the highest CNR (p < 0.05) that gives the best image quality. Among the implant materials tested, titanium Grade 5 has the highest levels of CNR while Zirconium has the lowest (p < 0.05). CONCLUSIONS: The optimum protocol for radiographic follow-up in areas near implants on the I-CAT is low-resolution settings (0.3 and 0.4 mm voxel sizes) which gave the highest CNR thus image quality. In presence of Zr implants, an alternative imaging modality (i.e., MRI) may be considered to avoid low-quality images.

Comparison of findings of radiographic and fractal dimension analyses on panoramic radiographs of patients with early-stage and advanced-stage medication-related osteonecrosis of the jaw.

OBJECTIVES: The aim of this study was to compare the panoramic radiographs of patients with early-stage and advanced-stage medication-related osteonecrosis of the jaw (MRONJ) for differences in radiographic findings and fractal dimension (FD). STUDY DESIGN: Data were collected from the medical records of 66 patients confirmed as having MRONJ. Panoramic radiographs of 66 patients (group I; without bone exposure; and group II; with bone exposure) were evaluated for the following signs; osteolysis, cortical erosion, focal and diffuse sclerosis, sequestrum, lamina dura thickening, enhancement of the inferior alveolar canal (IAC), persistent alveolar socket, pathologic fractures, and enhancement of the external oblique ridge. FD values were also compared between groups. RESULTS: The signs of focal and diffuse sclerosis, sequestrum, and enhancement of the IAC were observed significantly more often in group II than group I (P < .05). The mean FD values were 1.42 ± 0.11 in group I and 1.44 ± 0.18 in group II and were significantly different only in 1 region but not significantly different overall. CONCLUSIONS: Radiographic alterations of bone structures appeared more frequently in patients with advanced stages of MRONJ. No significant difference was detected in the FD values among the tested regions except the cancellous bone above the mandibular canal on the distal side of the mental foramen.

Cone Beam Computed Tomographic Evaluation of Intracranial Physiologic Calcifications.

OBJECTIVE: The aim of the present study was to evaluate the incidence of physiologic intracranial calcifications detected in cone beam computed tomography (CBCT) images of a Turkish subpopulation. METHODS: The CBCT image of the full head of 573 patients taken between 2015 and 2018 was evaluated retrospectively. The prevalence of habenular calcification, petroclinoid ligament, coroid plexus, interclinoid ligament (ICL), and carotico-clinoid ligament (CCL) calcifications was investigated. The age and gender of the patients were recorded. RESULTS: Intracranial calcification was found in 190 (33.1%) of 573 cases. The frequency of physiological calcifications is respectively; 19.2% were found as habenular, 4.88% as ICL, 3.83% as CCL, 2.7% as petroclinoid ligament, and 2.4% as choroid plexus. 38.2% of the women and 29.3% of the men had intracranial calcification. In 4 patients, both ICL and CCL ossification were detected. No statistically significant relationship was found between age, gender, and calcifications. CONCLUSION: Cone beam computed tomography is a widely used imaging technique for dental diagnosis and treatment. Intracranial physiological calcifications may be a common incidental finding of CBCT scans.

Trabecular structure designation using fractal analysis technique on panoramic radiographs of patients with bisphosphonate intake: a preliminary study.

OBJECTIVE: This study was performed to evaluate the trabecular pattern of patients with cancer taking bisphosphonates on panoramic images using fractal dimension (FD) analysis by comparison with healthy subjects and to assess whether any difference exists between regions. METHODS: FD analysis was conducted using ImageJ 1.3 software (National Institutes of Health, Bethesda, MD, USA) with the box-counting method on panoramic radiographs of 33 patients taking bisphosphonates (13 males and 20 females) and 33 healthy sex- and age-matched individuals. RESULTS: FD values were higher (1.39 ± 0.14) in the study group than control group (1.38 ± 0.07) (p ≤ 0.05). No difference was detected in the FD values among the tested regions. The mean FD values in the control and study groups were as follows: region 1, 1.49 and 1.41 (p = 0.54); region 2, 1.36 and 1.37 (p = 0.84); region 3, 1.35 and 1.42 (p = 0.11); and region 4, 1.39 and 1.39 (p = 0.90), respectively. Female patients showed significantly lower values above the mandibular canal on the distal side of the second premolar and anterior to the mental foramen than did male patients (p ≤ 0.05). Age was unrelated to the FD in the study group (p ≥ 0.05). CONCLUSIONS: The FD values of the patients with cancer taking bisphosphonates were higher than those of the controls. FD analysis showed the potential for examining bone structure in panoramic radiographs. Studies with a larger sample size are necessary to confirm these results.

Comparison of Cone Beam Computed Tomography and ultrasonography with two types of probes in the detection of opaque and non-opaque foreign bodies.

AIM: The aim of this study was to compare the diagnostic accuracy of intra-oral and extra-oral ultrasonographic (US) examinations performed with linear and convex probes in the detection of opaque and non-opaque foreign bodies (FBs) located in the maxillofacial area. MATERIALS AND METHODS: Thirteen different type of FBs were inserted into a sheep's head: a) on the external bone surface of mandible (between the mandibular corpus and masseter muscle), b) in the intrinsic muscular tissue (in the dorsum of the tongue) and c) in the hollow structures (into the maxillary sinus of the sheep's head). The FBs in muscle tissue were scanned intra-orally whereas FBs in bone external bone surface of mandible and in maxillary sinus were scanned both intra-orally and extra-orally. The sensitivity of cone beam computed tomography (CBCT) and US imaging methods in detection of FBs were compared for FBs on the bone surface and in the muscular tissue. RESULTS: The intra-observer kappa coefficients provided identical values of 0.236 for the extra-oral convex probe, 0.461 for the intra-oral linear probe for overall FBs detection, which indicated notably poor to fair intra-observer agreement. The inter-observer agreement showed a poor agreement for the extra-oral use of linear probe (0.341 and 0.393) and extra-oral use of convex probe (0.319 and 0.335), However, a fair agreement was determined for use of probe intra-orally (0.530 and 0.534). Overall, the diagnostic accuracy of the CBCT was higher than the US regarding the visualization of FBs in the bone tissue. CONCLUSION: US with a linear probe should be the first choice for the detection of the low-radiodensity FBs, which are entrapped in the soft tissue. However, CBCT is a more sensitive technique for the visualization of FBs in air and bone tissue compared to the US, particularly for the diagnosis of high-radiodensity FBs.

Evaluation of Anatomical and Volumetric Characteristics of the Nasopalatine Canal in Anterior Dentate and Edentulous Individuals: A CBCT Study.

OBJECTIVE: To examine the nasopalatine canal (NPC) anatomical and volumetric measurements in anterior edentulous (AE) and anterior dentate (AD) individuals and to compare these findings according to sex, age, shape, and severity of resorption in the premaxilla. METHODS: Two hundred cone beam computed tomography images were divided into 2 groups: AE and AD. The diameter, the length of the NPC and the width, the length of the buccal bone anterior to the NPC were measured and recorded. Linear and volumetric measurement results were evaluated in terms of age, sex, dental status, shape, and severity of resorption. RESULTS: No significant differences were observed between the AE and AD groups in terms of the NPC volume (P = 0.289). In the AE group, the spindle shape had the highest volume, and in the same group, with aging, the volume significantly increased (P = 0.00). The mean NPC volume was found to be statistically significantly larger in males than females (P = 0.02). A statistically significant relation was observed between NPC volume and resorption status. CONCLUSION: Severe bone resorption due to sustained edentation complicated implant surgery because of the increase in incisive and nasal foramen diameters and decrease in buccal residual bone dimensions. The NPC volume was found fewer in edentulous patients, and by the resorption, the volume was decreased.

Comparison of fractal dimension analysis and panoramic-based radiomorphometric indices in the assessment of mandibular bone changes in patients with type 1 and type 2 diabetes mellitus.

OBJECTIVES: This study compared the fractal dimension (FD) and radiomorphometric indices in the assessment of mandibular bone of patients with type 1 (T1 DM) and type 2 diabetes mellitus (T2 DM). STUDY DESIGN: Panoramic radiographs of 104 patients were evaluated to calculate FD, mandibular cortical width (MCW), panoramic mandibular index (PMI), and mandibular cortical index (MCI) in the mandible. RESULTS: No statistically significant differences were found in FD when T1 DM and T2 DM groups were compared with controls (P ≥ .168). Patients with T1 DM had significantly lower MCW (P < .001) and PMI (P = .030) compared with controls. Patients with T2 DM had no significant differences in MCW (P = .228) or PMI (P = .137) compared with controls. No significant differences were observed between patients with T1 DM and those with T2 DM for FD, MCW, and PMI (P > .05). In the T1 DM and T2 DM groups, there was a significant correlation between MCW and FD (P ≤ .011). No correlation was observed between FD and PMI in either the T1 DM group or the T2 DM group (P ≥ .142). No significant differences in MCI were observed between the DM groups and controls (P = .740) or between the T1 DM and T2 DM groups (P = 1.000). CONCLUSIONS: The cortical and trabecular bone architectures of patients with T1 DM and T2 DM were not different. Patients with T1 DM had lower cortical measurements compared with controls.

Anatomic Study on Sphenoidal Emissary Foramen by Using Cone-Beam Computed Tomography.

OBJECTIVES: The goal of this retrospective study is to evaluate the radiologic anatomy of sphenoidal emissary foramen (SEF) by using cone-beam computed tomography (CBCT) scans. METHODS: Three hundred seventeen (189 female and 128 male) full-head CBCT images were evaluated in this study. Incidence, diameter, shape, confluence to foramen ovale, and distance to anatomic structures of SEF were noted. RESULTS: In the 317 analyzed images, the SEF was identified in 89 (28.1%) images. Of these, 67 (21.1%) were unilateral, 22 were (6.9%) bilateral. The maximum mean diameter of SEF was measured 2.66 mm on the right side and 2.82 mm on the left side (P = 0.16). The most observed SEF shape was oval with the incidence of 68.5% (P ≤ 0.05). Confluence was observed in 23.4% of SEF whereof 84.6% were in the left side (P ≤ 0.05). CONCLUSION: Observations in this study tender new anatomic parameters regarding SEF incidence, characteristics, and distances to proximate anatomic structures. Knowledge related to SEF variations will be helpful for neurosurgeons and radiologist.

Evaluation of the Characteristics and Association Between Schneiderian Membrane Thickness and Nasal Septum Deviation.

OBJECTIVE: Nasal septum deviation (NSD) is an anomaly that disturbs normal mucus drainage in sinuses, leading to recurrent sinusitis. Sinusitis, infections, and mucosal irritations are the potential causes of Schneiderian membrane thickening (SMT). The aim of this study was to evaluate the characteristics and association between NSD and SMT along with factors such as age, gender, and tooth groups using cone-beam computed tomography (CBCT) imaging. METHODS: The maxillary sinus and nasal cavity of 249 patients (136 females and 113 males) were examined retrospectively using CBCT. The statistical analysis was performed to determine the association between SMT, NSD, gender, and age. RESULTS: No statistically significant relation was detected between NSD and SMT. The NSD was found in 50.6% of patients without gender predilection. Age was not associated with the presence of NSD. The mean thickness of the membrane was least in the third molar region and highest in the first molar region. The average SMT was found to be higher in males for all the examined tooth areas (P ≤ 0.05). CONCLUSION: A retrospective evaluation of CBCT images emphasized the concept that NSD was not a factor that affected the thickening of maxillary sinus mucosa. The CBCT imaging could be used for evaluating the maxillary sinuses and nasal septum.

The correlation between mothers' participation in infant care in the NICU and their anxiety and problem-solving skill levels in caregiving.

OBJECTIVE: To examine the correlation between mothers' participation in infant care in the Neonatal Intensive Care Unit (NICU) and their anxiety and problem-solving skill levels in caregiving. METHODS: The cross-sectional study was conducted with 340 mothers whose babies were in the NICU. Data were collected with a questionnaire, a Participation in Caregiving Observation Form, the State and Trait Anxiety Inventory and the Problem-solving Skills Evaluation Form. Descriptive statistics and correlation analysis were used in the evaluation of the data. RESULTS: The mothers were with their babies an average of 6.28 ± 2.43 (range: 1-20) times a day, participating in many basic procedures of care. A negative correlation was found between the mothers' scores on the Participation in Caregiving Observation Form and their State and Trait Anxiety Inventory scores (respectively, r = -0.48, p < 0.001 and r = -0.12, p < 0.05), but a positive correlation was observed between the Problem-solving Process (r = 0.41, p < 0.001) and the Baby Care Skills (r = 0.24, p < 0.001) Subscale scores. CONCLUSIONS: The study revealed that mothers participated in many basic caregiving procedures in the NICU and this participation resulted in reduced state and trait anxiety levels and an improvement in the mothers' problem-solving skills with respect to baby care and related problems.

Oscillatory responses representing differential auditory processing in sleep.

The goal of the study was to investigate the contribution of the delta and theta responses to the peaks on the event-related potential waveform and specifically to find the possible cognitive correlates of these oscillatory responses in rapid eye movements (REM) sleep and Stage 2 (spindle sleep), Stage 3 (light sleep) and Stage 4 (deep sleep; slow wave sleep) of non-REM sleep. Data on overnight sleep was acquired from 12 healthy, young adult, volunteer males; those on awake stage were obtained from 19 matched males. Brain activity was obtained in response to auditory stimuli (2000 Hz deviant and 1000 Hz standard stimuli: 65 dB, 10 ms r/f time, 50 ms duration) under passive oddball paradigm in sleep, active and passive oddball (OB-a, OB-p, respectively) paradigms in wakefulness. The effect of the experimental variables (stimulus type, sleep stage) was studied using 2 x 4 analysis of variance for repeated measures and stepwise multiple regression analysis. Overall, three types of configurations were obtained for the oscillatory responses which varied according to sleep stage and stimulus type: Large amplitude, differentiated delta and distinct theta response of long duration; distinct theta response with short duration; distinct delta response. As in wakefulness, the morphology of the time-domain peaks was found to be due to the superposition of the delta and theta responses. The configuration in REM resembled the responses to the OB-p paradigm and that NREM stages resembled the responses to the OB-a paradigm in wakefulness. Auditory information processing selectively varied according to sleep stages and took longer in sleep. Comparable peaks were obtained at longer latencies and later components appeared that did not exist under wakefulness. With respect to the long-duration theta activity, and greater differentiation between the deviant- and standard-elicited stimuli, Stage 2 appeared to represent the more effortful cognitive processing.

Early gamma response of sleep is sensory/perceptual in origin.

The goal of the study was to investigate the gamma response of the brain and its functional correlates in rapid eye movements (REM) sleep and the three stages of non-REM sleep. Data on overnight sleep were acquired from 16 healthy, young adult, volunteer males. Neuroelectric activity was recorded from seven recording sites (Fz, Cz, Pz, F3, F4, P3, P4) in response to auditory stimuli (2000 Hz deviant and 1000 Hz standard stimuli: 65 dB, 10 ms r/f time, 50 ms duration) under passive oddball paradigm. Data were analyzed with the Fourier transform and digital filtering and also the recently developed technique of time-frequency component analysis (TFCA). TFCA displayed the gamma response under all stages of sleep. Statistical analysis did not reveal a significant effect of stimulus type, recording site or sleep stage on the three parameters of TFCA, which included maximum value of the time-frequency representation of the extracted gamma component, maximum magnitude of the time-domain representation of the component and the energy of this component. The gamma period included N1 and the early theta response, both of which are related to sensory-perceptual processing in the literature. According to these findings, the gamma response is possibly related, as in wakefulness, to early stimulus processing that also includes sensory/perceptual operations.

Early time-locked gamma response and gender specificity.

The aim was to investigate whether gender is a causative factor in the gamma status according to which some individuals respond with time-locked, early gamma response, G+, while the others do not show this response, G-. The sample consisted of 42 volunteer participants (between 19 and 37 years of age with at least 9 years of education). There were 22 females and 20 males. Data were collected under the oddball paradigm. Auditory stimulation (10 ms r/f time, 50 ms duration, 65 dB SPL) consisted of target (2000 Hz; p = .20) stimuli that occurred randomly within a series of standard stimuli (1000 Hz; p = .80). Gamma responses were studied in the amplitude frequency characteristics, in the digitally filtered event-related potentials (f-ERPs) and in the distributions which were obtained using the recently developed time-frequency component analysis (TFCA) technique. Participants were classified into G+ and G- groups with a criterion of full agreement between the results of an automated gamma detection technique and expert opinion. The 2 x 2 x 2 ANOVA on f-ERPs and 2 x 2 x 2 multivariate ANOVA on TFCA distributions showed the main effect of gamma status and gender as significant, and the interaction between gamma status and gender as nonsignificant. Accordingly, individual difference in gamma status is a reliable phenomenon, but this does not depend on gender. There are conflicting findings in the literature concerning the effect of gender on ERP components (N100, P300). The present study showed that if the gamma status is not included in research designs, it may produce a confounding effect on ERP parameters.

Time-frequency component analyser and its application to brain oscillatory activity.

Currently, event-related potential (ERP) signals are analysed in the time domain (ERP technique) or in the frequency domain (Fourier analysis and variants). In techniques of time-domain and frequency-domain analysis (short-time Fourier transform, wavelet transform) assumptions concerning linearity, stationarity, and templates are made about the brain signals. In the time-frequency component analyser (TFCA), the assumption is that the signal has one or more components with non-overlapping supports in the time-frequency plane. In this study, the TFCA technique was applied to ERPs. TFCA determined and extracted the oscillatory components from the signal and, simultaneously, localized them in the time-frequency plane with high resolution and negligible cross-term contamination. The results obtained by means of TFCA were compared with those obtained by means of other commonly used techniques of ERP analysis, such as bilinear time-frequency distributions and wavelet analysis. It is suggested that TFCA may serve as an appropriate tool for capturing the localized ERP components in the time-frequency domain and for studying the intricate, frequency-based dynamics of the human brain.