Physiological and Psychological Effects of Volatile Organic Compounds from Dried Common Rush (Juncus effusus L. var. decipiens Buchen.) on Humans.

This study compared the participants' physiological responses and subjective evaluations of air scented with different concentrations of common rush (Juncus effusus L. var. decipiens Buchen.) (30 g and 15 g, with fresh air as a control). We asked 20 participants to complete a series of visual discrimination tasks while inhaling two different air samples. We evaluated (1) brain activity, (2) autonomic nervous activity, and (3) blood pressure and pulse rate, (4) in combination with self-evaluation. In addition, we quantified the concentrations of volatile organic compounds. The participants reported the scent to be sour, pungent, and smelly; this impression was likely caused by hexanal and acetic acid. Although the self-evaluations showed that participants did not enjoy the scent, their alpha amplitudes of electroencephalogram and parasympathetic nervous activity were increased, suggesting that participants were relaxed in this atmosphere. Moreover, a lower concentration resulted in a greater induction of relaxation. While the air was not pleasant-smelling, the volatile organic compounds present had a positive psychophysiological impact.

Differential roles of spatial frequency on reading processes for ideograms and phonograms: a high-density ERP study.

The neural substrate of the dissociation between reading Japanese ideograms (Kanji) and phonograms (Kana) is currently unclear. To test whether spatial frequency (SF) information is responsible for this phenomenon, we recorded high-density event-related potentials (ERPs) with unfiltered or spatially filtered word stimuli in Japanese-speaking subjects. Kanji (early-learned, late-learned), Kana (word, non-word), and scrambled characters served as stimuli. Fourier analysis revealed that Kanji and Kana were characterized by high-SF (HSF) and low-SF (LSF) information, respectively. In ERPs with unfiltered stimuli, bilateral occipital P100, left occipitotemporal N170 and fronto-central N400 were elicited. Scrambled characters did not evoke left-lateralized N170 or clear N400. Under the LSF condition, P100 and N170 latencies for Kanji were significantly longer than those for Kana. In the HSF condition, P100 and N170 latencies for late-learned Kanji were significantly longer than those for early-learned Kanji. There was no significant difference in the N400 between Kanji and Kana in both SF conditions. These results suggest that early visual responses, but not the semantic component, are influenced by SF. This indicates a close link between Kana and LSF information, and between Kanji and HSF information. The differential effects of SF could underlie the neural basis of the differences between Kanji and Kana reading.

Neural responses in the occipital cortex to unrecognizable faces.

OBJECTIVE: Event-related potentials (ERPs) were recorded to examine neural responses to face stimuli in a masking paradigm. METHODS: Images of faces (neutral or fearful) and objects were presented in subthreshold, threshold, and suprathreshold conditions (exposure durations of approximately 20, 30 and 300 ms, respectively), followed by a 1000-ms pattern mask. We recorded ERP responses at Oz, T5, T6, Cz and Pz. The effects of physical stimulus features were examined by inverted stimuli. RESULTS: The occipital N1 amplitude (approximately 160 ms) was significantly smaller in response to faces than objects when presented at a subthreshold duration. In contrast, the occipitotemporal N170 amplitude was significantly greater in the threshold and suprathreshold conditions compared with the subthreshold condition for faces, but not for objects. The P1 amplitude (approximately 120 ms) elicited by upright faces in the subthreshold condition was significantly larger than for inverted faces. CONCLUSIONS: P1 and N1 components at Oz were sensitive to subthreshold faces, which suggests the presence of fast face-specific process(es) prior to face-encoding. The N170 reflects the robustness of the face selective response in the occipitotemporal area. SIGNIFICANCE: Even when presented for a subthreshold duration, faces were processed differently to images of objects at an early stage of visual processing.

Decreased spatial frequency sensitivities for processing faces in male patients with chronic schizophrenia.

OBJECTIVE: Schizophrenia impairs early visual cognitive processing. Low and high spatial frequency (LSF, HSF) visual information are differentially processed in humans. We investigated whether electrophysiological abnormalities exist in visual processing for spatial frequency (SF)-filtered neutral/emotional faces in schizophrenics. METHODS: Subjects consisted of 16 male chronic schizophrenics and 23 controls. Event-related potentials (ERPs) to SF-filtered (LSF or HSF) and unfiltered (broad SF; BSF) pictures of neutral, happy, and fearful faces were recorded at 20 scalp sites. The relationships between the P100 (P1)/N170 amplitudes and the Global Assessment of Functioning (GAF) scores in patients were also evaluated. RESULTS: For the P1 amplitudes at O1/O2, controls exhibited a significant LSF>BSF difference, while schizophrenics showed no LSF>BSF difference. For the N170 amplitudes at T5/T6, controls revealed a significant HSF>BSF difference, while schizophrenics showed no such difference. For the P1 latencies, controls but not schizophrenics showed a significant difference (LSF>BSF=HSF). For the N170 latencies, no significant SF differentiation was found between the two groups. For both P1 and N170 amplitudes, no significant effects of facial expressions were observed in controls and patients regardless of SFs. There were significant negative correlations between the GAF scores and the N170 amplitudes to BSF faces in schizophrenics, but not for P1 amplitudes. CONCLUSIONS: Schizophrenics showed abnormal P1 and N170 responses to SF changes in faces, thus indicating decreased SF sensitivities for processing of faces. SIGNIFICANCE: Abnormal early visual processing may underlie some of the deficits associated with face recognition in schizophrenia.

Early ERP components differentially extract facial features: evidence for spatial frequency-and-contrast detectors.

It is generally accepted that the N170 component of an event-related potential (ERP) reflects the structural encoding of faces and is specialized for face processing. Recent neuroimaging and ERP studies have demonstrated that spatial frequency is a crucial factor for face recognition. To clarify which early ERP components reflect either coarse (low spatial frequency, LSF) or fine (high spatial frequency, HSF) processing of faces, we recorded ERPs induced by manipulated face stimuli. By filtering the original grayscale faces (broadband spatial frequency) spatially, we created LSF and HSF face stimuli. Next, we created physically equiluminant (PEL) face stimuli to eliminate the effects of lower order information, such as luminance and contrast. The P1 amplitude at the occipital region was augmented by LSF faces, while the N170 amplitude increased for HSF faces. The occipital P1 amplitude for PEL faces was relatively unaffected compared with that for PEL houses. In addition, the occipital N2 for PEL faces was spatiotemporally separable from N170 in a time-window between P1 and N170. These results indicate that P1 reflects coarse processing of faces, and that the face robustness further assures face-specific processing in the early component. Moreover, N2 reflects the early contrast processing of faces whereas N170 analyzes the fine facial features. Our findings suggest the presence of spatial frequency-and-contrast detectors for face processing.

Different perceptual sensitivities for Chernoff's face between children and adults.

The aim of this study was to investigate the differences between children and adults in recognizing facial expressions of simple line drawings of "Chernoff's face". First, the angles of the eyebrows and mouth of Chernoff's face were changed in a stepwise way with a personal computer, and the emotional response of the subjects was evaluated by a questionnaire. Second, three drawings of non-target stimuli (neutral face, angry face, and wheelchair) and target stimuli were used to elicit event-related potentials (ERPs). Children had higher scores for the facial expressions than adults, and relied much more on the angles of the eyebrows and mouth. The major ERP findings were (1) the latencies of P100 and N170 were significantly longer in children than adults, (2) the amplitudes of P100 were significantly larger in children than adults, but the N170 amplitudes were not significantly different, and (3) a slow negative shift was recorded with a latency of 240-460ms at the posterior-temporal site for angry face compared with neutral face in adults but not in children. These results suggest that the differences in the electrophysiological recognition of facial expressions can be set at 240ms after appearance of the Chernoff's face in adults but not in children.

The relationship between retrieval success and task performance during the recognition of meaningless shapes: an event-related near-infrared spectroscopy study.

Retrieval success of episodic memory has been studied intensively through the investigation of old/new effects. Recognized stimuli used in event-related functional magnetic resonance imaging studies on old/new effects have been words and visual materials which can evoke semantic associations. To elucidate the neural basis of retrieval success uninfluenced by semantic processing, we investigated the correlation between old/new effects and task performance during the recognition of meaningless shapes, by using event-related near-infrared spectroscopy. Forty-two right-handed subjects made recognition judgments about old (studied) or new (unstudied) meaningless shapes. The old/new effects of the shapes were positively correlated with task performance in the bilateral inferior lateral parietal cortex (ILP), but predominantly in the left ILP. This finding indicated that the ILP was directly associated with retrieval success and its lateralization was consistently left-sided irrespective of the type of stimulus.

Familiarity facilitates the corticocortical processing of face perception.

The visual evoked potentials elicited by mosaic pictures were used to elucidate the initial step of face perception. Three different mosaic levels (subthreshold, threshold, suprathreshold) for familiar and unfamiliar faces and objects were randomly presented for 250 ms. The latencies of occipital N1 and posterior-temporal N2 were shortened by decreasing the mosaic levels of faces but not for object. The N2 amplitude significantly increased at threshold and suprathreshold levels for familiar and unfamiliar faces. The latency difference between N1 and N2 at threshold level for a familiar face was significantly shortened compared with that for an unfamiliar face. Our findings suggest the initial step of face perception is already set in the primary visual cortex, and familiarity can facilitate the corticocortical processing of face information.