Deliberate self-harm in children and adolescents: a research update

PURPOSE OF REVIEW: We outline research developments in 2004 and early 2005 published in English language journals on deliberate self-harm among children and adolescents up to the age of 18 years. RECENT FINDINGS: The main issue of concern in recent times has been the risk/benefit profile of using antidepressants, especially selective serotonin reuptake inhibitors, in depressed children and adolescents. Other important topics include treatment approaches, particularly cognitive behaviour therapy, dialectical behaviour therapy and multisystemic therapy, barriers to help seeking, the Internet and prevention. SUMMARY: Rates of deliberate self-harm appear to be rising among young people. Risk factors associated with deliberate self-harm are becoming clearer and the evaluation of treatments is progressing. However, the recent conflicting evidence and guidelines regarding selective serotonin reuptake inhibitors and suicidality are presenting major difficulties for clinicians. The role of the Internet and initiatives to prevent suicidal behaviour in adolescents require further research.     

Electrosensory interference in naturally occurring aggregates of a species of weakly electric fish, Eigenmannia virescens

The detection and identification of behaviorally relevant signals in the presence of competing signals in the environment is a major challenge of animal sensory systems. In weakly electric fish such as Eigenmannia virescens, the interactions between the autogenous electric field and the electric fields of nearby conspecifics can have profound effects on the perception of other behaviorally relevant electrosensory information. To better understand the natural signals that the nervous system of Eigenmannia experiences during the processing of electrosensory information, we examined the electrosensory milieu of Eigenmannia in the wild and in the laboratory. Recordings of the electric fields of Eigenmannia were made in 'black' and 'white' waters near the Napo River in eastern Ecuador. Fourier analysis revealed that Eigenmannia typically experience the electric fields of three to five conspecifics during the day and night in each habitat. The median difference in electric organ discharge frequencies between nearby Eigenmannia during the day was 23 Hz in black water habitats, 41 Hz in white water, and 37 Hz at night in both habitats: these signals are known to activate tuberous electroreceptors and downstream CNS circuits. There was no correlation between the number of individual Eigenmannia detected at recording sites and electric organ discharge frequencies. Further, Eigenmannia apparently do not maximize the frequency differences between conspecifics. In laboratory studies fish were preferentially observed in aggregates of two fish or more. Aggregate sizes observed in the laboratory were similar to those in the wild.     

Light- and clock-dependent regulation of ribosomal S6 kinase activity in the suprachiasmatic nucleus

Recent work has revealed that signalling via the p42/44 mitogen-activated protein kinase (MAPK) pathway couples light to entrainment of the circadian clock located in the suprachiasmatic nucleus (SCN). Given that many effects of the MAPK pathway are mediated by intermediate kinases, it was of interest to identify kinase targets of ERK in the SCN. One potential target is the family of 90-kDa ribosomal S6 kinases (RSKs). In this study, we examined light-induced regulation of RSK-1 in the SCN. Immunohistochemical and Western analysis were used to show that photic stimulation during the early and late night triggered the phosphorylation of RSK-1 at two sites that are targeted by ERK. This increase in the phosphorylation state of RSK-1 corresponded with an approximate fourfold increase in kinase activity. Light exposure during the subjective day did not increase the phosphorylated form of RSK-1, indicating that the capacity of light to stimulate RSK-1 activation is phase-restricted. Double immunofluorescent labelling of SCN tissue revealed the colocalized expression of the activated form of ERK with the phosphorylated form of RSK-1 following a light pulse. In vivo pharmacological inhibition of light-induced MAPK pathway activation blocked RSK-1 phosphorylation, indicating that RSK-1 activity is regulated by the MAPK pathway. PDK-1, a coregulator of RSK-1, is also expressed in the SCN and is likely to contribute to RSK-1 activity. RSK-1 phosphorylation was also rhythmically regulated within a subset of phospho-ERK-expressing cells. Together these results identify RSK-1 as a light- and clock-regulated kinase and raise the possibility that it contributes to entrainment and timing of the circadian pacemaker.     

Normative ranges and specificity of the multifocal VEP

Purpose: To describe a normative database for the multifocal VEP (mfVEP) and to evaluate specificity for a range of cluster criteria. Methods: One hundred persons (62 females and 38 males) with normal visual fields and ranging in age from 21.6 to 92.4 years participated in this study. Self-reported race in 80 of these 100 persons was `White or Caucasian,' eight were `Black or African-American,' eight were `Asian,' and four were `Hispanic or Latino.' Pattern-reversal mfVEPs were obtained using a dartboard stimulus pattern in VERIS^TM and two 8-min runs per eye were averaged. A bootstrap technique was used to estimate the normal range of mfVEP response signal-to-noise ratio (SNR) and inter-ocular amplitude ratio at each location. Specificity (1 – false alarm rate) was evaluated for a range of cluster criteria, whereby the number and probability level of the points defining a cluster were varied. Results: There was no overall effect of age on SNR (r ²=0.16, p=0.22) nor was the interaction between age and location significant (F=0.83, p=0.82, ANOVA). The location with the largest age effect had an r ² of only 0.13. There was a small but significant effect of sex (t=2.1, p=0.04) such that SNR was slightly (11) larger in females than males, but there was no significant interaction between sex and age (t=0.82, p=0.41). There was a slight trend toward higher SNR in the Asian group and lower SNR in the African-American group, but the overall effect of race was not significant (F=1.99, p=0.12). Specificity depended on the number and probability level of the points defining a cluster. Specificity did not vary by age group in a simple monotonic manner. False positive rates were slightly higher in females than males, and slightly higher in the African-American group as compared with the Asian group. Conclusions: Excellent specificity can be achieved for the mfVEP by using particular cluster criteria for monocular and inter-ocular tests. The effects of age, sex, and race were all very small and only the effect of sex was statistically significant. This normative database can be used for analyses of mfVEP results from individual patients with little risk that demographic factors such as age and sex will confound diagnostic accuracy.     

Voltage-gated Na+ channels enhance the temporal filtering properties of electrosensory neurons in the torus

Regenerative processes enhance postsynaptic potential (PSP) amplitude and behaviorally relevant temporal filtering in more than one-third of electrosensory neurons in the torus semicircularis of Eigenmannia. Data from in vivo current-clamp intracellular recordings indicate that these "regenerative PSPs" can be divided in two groups based on their half-amplitude durations: constant duration (CD) and variable duration (VD) PSPs. CD PSPs have half-amplitude durations of between 20 and 60 ms that do not vary in relation to stimulus periodicity. In contrast, the half-amplitude durations of VD PSPs vary in relation to stimulus periodicity and range from approximately 10 to 500 ms. Injection of 0.1 nA sinusoidal current through the recording electrode demonstrated that CD PSPs and not VD PSPs can be elicited by voltage fluctuations alone. In addition, CD PSPs were blocked by intracellular application of either QX-314 or QX-222, whereas VD PSPs were not. These in vivo data suggest, therefore, that CD PSPs are mediated by voltage-dependent Na+ conductances.     

Appearance of the frequency doubling stimulus in normal subjects and patients with glaucoma

PURPOSE: To determine whether the spatial structure of the frequency doubling technology (FDT) perimetry stimulus is visible at detection-contrast threshold in normal observers and those with glaucoma and to assess its perceived spatial frequency at threshold and suprathreshold contrast. METHODS: Three subject groups were assessed: 10 young normal observers (aged <40 years), 10 older normal observers (aged >50 years), and 10 subjects with glaucoma. Detection thresholds for centrally and eccentrically presented 10 degrees squares, 0.25-cyc/deg, 25-Hz counterphase flicker sine-wave gratings were obtained by using a yes-no staircase procedure. Eccentric locations were in areas of loss of FDT sensitivity (< or =21 degrees ) in subjects with glaucoma, or at 7 degrees or 21 degrees inferonasally in normal observers. Resolution-contrast thresholds were determined by a two-alternative, forced-choice staircase procedure in which subjects selected the orientation of the grating stimulus tilted at +/-45 degrees. Perceived spatial frequency was determined by having subjects alter the spatial frequency of a temporally interleaved stationary sine-wave grating to match the FDT stimulus. RESULTS: No significant difference was found between detection- and resolution-contrast thresholds, implying that spatial structure was visible at detection threshold. In general, subjects perceived the spatial structure to have a spatial frequency closer to doubled than to veridical, although the young normal subjects reported a lower apparent spatial frequency than older individuals. CONCLUSIONS: When instructed as for clinical testing, subjects respond to the presence of the structure of the grating, and perceive the FDT stimulus to have a spatial frequency greater than its true spatial frequency. These findings were consistent across both normal observers and those with glaucoma, at both central and eccentric test locations.