Learning with conviction: Exploring the relationship between criminal legal system involvement and substance use and recovery outcomes for students in collegiate recovery programs

This study examines the association of criminal legal system involvement and age with substance use and academic related outcomes among students involved in collegiate recovery programs in the US. We examined 435 students in collegiate recovery using a national survey of college students. We computed differences between non-system-involved, system-involved with no incarceration history, and formerly incarcerated participants on relevant substance use and recovery-related outcomes. The results provide evidence that there are significant differences between those system-involved and those who are not. Specifically, we found significant differences across the outcomes of recovery capital, quality of life, hours worked per week, and substance use disorder symptoms, but after controlling for relevant covariates, only the differences between hours worked (non-system involved and system involved < formerly incarcerated) and substance use disorder symptoms (non-system involved < system involved and formerly incarcerated) remained significant. The study contributes to the literature by demonstrating that nearly half of the collegiate students in recovery in this sample have legal system-involvement and a third have been incarcerated. Further, interventions for collegiate recovery programs may need to be adjusted to account for legal system involvement among their members.

A random-matrix theory of the number sense

Number sense, a spontaneous ability to process approximate numbers, has been documented in human adults, infants and newborns, and many other animals. Species as distant as monkeys and crows exhibit very similar neurons tuned to specific numerosities. How number sense can emerge in the absence of learning or fine tuning is currently unknown. We introduce a random-matrix theory of self-organized neural states where numbers are coded by vectors of activation across multiple units, and where the vector codes for successive integers are obtained through multiplication by a fixed but random matrix. This cortical implementation of the 'von Mises' algorithm explains many otherwise disconnected observations ranging from neural tuning curves in monkeys to looking times in neonates and cortical numerotopy in adults. The theory clarifies the origin of Weber-Fechner's Law and yields a novel and empirically validated prediction of multi-peak number neurons. Random matrices constitute a novel mechanism for the emergence of brain states coding for quantity.This article is part of a discussion meeting issue 'The origins of numerical abilities'.

Seeing more than meets the eye: processing of illusory contours in animals

This review article illustrates that mammals, birds and insects are able to perceive illusory contours. Illusory contours lack a physical counterpart, but monkeys, cats, owls and bees perceive them as if they were real borders. In all of these species, a neural correlate for such perceptual completion phenomena has been described. The robustness of neuronal responses and the abundance of cells argue that such neurons might indeed represent a neural correlate for illusory contour perception. The internal state of an animal subject (i.e., alert and behaving) seems to be an important factor when correlating neural activity with perceptual phenomena. The fact that the neural network necessary for illusory contour perception has been found in relatively early visual brain areas in all tested animals suggests that bottom-up processing is largely sufficient to explain such perceptual abilities. However, recent findings in monkeys indicate that feedback loops within the visual system may provide additional modulation. The detection of illusory contours by independently evolved visual systems argues that processing of edges in the absence of contrast gradients reflects fundamental visual constraints and not just an artifact of visual processing.

Release from masking in fluctuating background noise in a songbird's auditory forebrain

Fluctuations in the ubiquitous masking background noise can be exploited by the vertebrate auditory system to considerably improve signal detection. Here we demonstrate neuronal masking release in amplitude-modulated background noise on the level of the European starling's auditory forebrain, an area that is the analogue of the mammalian primary auditory cortex. Tone-evoked responses in the presence of modulated and unmodulated maskers were recorded in unrestrained birds via radiotelemetry. Based on a rate code, the average amount of neuronal masking release was similar to that observed in a psychoacoustic study on the starling with stimuli confined to a single auditory filter. The results suggest that the neurons exploited predominantly temporal features of the acoustic background to improve signal detection.

Encoding of both vertical and horizontal disparity in random-dot stereograms by Wulst neurons of awake barn owls

In binocular vision, the lateral displacement of the eyes gives rise to both horizontal and vertical disparities between the images projected onto the left and right retinae. While it is well known that horizontal disparity is exploited by the binocular visual system of birds and mammals to enable depth perception, the role of vertical disparity is still largely unclear. In this study, neuronal activity in the visual forebrain (visual Wulst) of behaving barn owls to vertical disparity was investigated. Single-unit responses to global random-dot stereograms (RDS) were recorded with chronically implanted electrodes and transmitted via radiotelemetry. Nearly half of the cells investigated (44%, 16/36) varied the discharge as a function of vertical disparity. Like horizontal-disparity tuning profiles, vertical-disparity tuning curves typically exhibited periodic modulation with side peaks flanking a prominent main peak, and thus, could be fitted well with a Gabor function. This indicates that tuning to vertical disparity was not caused by disrupting horizontal-disparity tuning via vertical stimulus offset, but by classical disparity detectors whose orientation tuning was tilted. When tested with horizontal in addition to vertical disparity, almost all cells investigated (92%, 12/13) were tuned to both kinds of disparity. The emergence of disparity detectors sensitive in two dimensions (horizontal and vertical) is discussed within the framework of the disparity energy model.

Hierarchical processing of horizontal disparity information in the visual forebrain of behaving owls

According to their restricted receptive fields and input-filter characteristics, disparity-sensitive neurons at early processing levels of the visual system perform rather ambiguous computations; they respond vigorously to disparity in false-matched images and show multiple response peaks in their disparity-tuning profiles. On the other hand, the perception of depth from binocular disparity is reliable, thus raising the question as to where and how in the brain additional processing is accomplished leading toward behaviorally relevant disparity detection. To address this issue, tuning data during stimulation with correlated and anticorrelated random-dot stereograms (a-RDS) were obtained from 52 disparity-sensitive visual Wulst neurons in three behaving owls. From the disparity-tuning curves, several quantitative measures were derived that allowed to determine the response ambiguity of a cell. A systematic decline of response ambiguities with increasing response latencies was observed. An increase in response latencies of neurons was correlated with a decrease of the strength of responses to a-RDS. Declining responses to a-RDS are expected for global detectors, because an owl was not able to discriminate depth in psychophysical tests with a-RDS. In addition, suppression of response side peaks was increased and disparity tuning was enhanced with growing response latencies. These results suggest a functional hierarchy of disparity processing in the owl's forebrain, leading from spatial filters to more global disparity detectors that may be able to solve the correspondence problem. Nonlinear threshold operations and inhibition are proposed as candidate mechanisms to resolve coding ambiguities.

Signal detection in amplitude-modulated maskers. II. Processing in the songbird's auditory forebrain

In the natural environment, acoustic signals have to be detected in ubiquitous background noise. Temporal fluctuations of background noise can be exploited by the auditory system to enhance signal detection, especially if spectral masking components are coherently amplitude modulated across several auditory channels (a phenomenon called 'comodulation masking release'). In this study of neuronal mechanisms of masking release in the primary auditory forebrain (field L) of awake European starlings (Sturnus vulgaris), we determined and compared neural detection thresholds for 20-ms probe tones presented in a background of sinusoidally amplitude modulated (10-Hz) noise maskers. Responses of a total of 34 multiunit clusters were recorded via radiotelemetry with chronically implanted microelectrodes from unrestrained birds. For maskers consisting of a single noise band centred around the recording site's characteristic frequency, a substantial reduction in detection threshold (21 dB on average) was found when probe tones were presented during envelope dips rather than during envelope peaks. Such effects could also explain results obtained for masking protocols where the on-frequency noise band was presented together with excitatory or inhibitory flanking bands that were either coherently modulated (in-phase) or incoherently modulated (phase-shifted). Generally, masking release for probe tones in maskers with flanking bands extending beyond the frequency range of a cell cluster's excitatory tuning curve was not substantially improved. Only some of the neurophysiological results are in agreement with behavioural data from the same species if only the average population response is considered. A subsample of individual neurons, however, could account for behavioural thresholds.

Miniature stereo radio transmitter for simultaneous recording of multiple single-neuron signals from behaving owls

Wireless radiotelemetric transmission of neuronal activity is an elegant technique to study brain-behavior interaction in unrestrained animals. In the current study, a miniature FM-stereo radio transmitter is described that permitted simultaneous recordings from two microelectrodes in behaving barn owls. Input from two independent channels is multiplexed to form a stereo composite signal that modulates a radio frequency carrier. The high quality of broadcasted extracellular signals enabled separation of single units based on differences in spike waveforms. Recording several single cells from different electrodes allows the possibility of investigating correlations between small, distributed neuronal ensembles. Multi-channel radiotelemetry that meets the demands of modern electrophysiology might open a new perspective for combined behavioral/neurophysiological approaches in freely-behaving animals.

Horizontal-disparity tuning of neurons in the visual forebrain of the behaving barn owl

Stereovision plays a major role in depth perception of animals having frontally-oriented eyes, most notably primates, cats, and owls. Neuronal mechanisms of disparity sensitivity have only been investigated in anesthetized owls so far. In the current study, responses of 160 visual Wulst neurons to static random-dot stereograms (RDS) were recorded via radiotelemetry in awake, fixating barn owls. The majority of neurons (76%) discharged significantly as a function of horizontal disparity in RDS. The distribution of preferred disparities mirrored the behaviorally relevant range of horizontal disparities that owls can exploit for depth vision. Most tuning profiles displayed periodic modulation and could well be fitted with a Gabor function as expected if disparity detectors were implemented according to the disparity energy model. Corresponding to this observation, a continuum of tuning profiles was observed rather than discrete categories. To assess a possible clustering of neurons with similar disparity-tuning properties, single units, and multi-unit activity recorded at individual recording sites were compared. Only a minority of neurons were clustered according to their disparity-tuning properties, suggesting that neurons in the visual Wulst are not organized into columns by preferred disparity. To assess whether variable vergence eye movements influenced tuning data, we correlated tuning peak positions on a trial-by-trial basis for units that were recorded simultaneously. The general lack of significant correlation between single-trial peak positions of simultaneously recorded units indicated that vergence, if at all, had only a minor influence on the data. Our study emphasizes the significance of visual Wulst neurons in analyzing stereoscopic depth information and introduces the barn owl as a second model system to study stereopsis in awake, behaving animals.

Perception and neuronal coding of subjective contours in the owl

Robust form perception and underlying neuronal mechanisms require generalized representation of object boundaries, independent of how they are defined. One visual ability essential for form perception is reconstruction of contours absent from the retinal image. Here we show that barn owls perceive subjective contours defined by grating gaps and phase-shifted abutting gratings. Moreover, single-neuron recordings from visual forebrain (visual Wulst) of awake, behaving birds revealed a high proportion of neurons signaling such subjective contours, independent of local stimulus attributes. These data suggest that the visual Wulst is important in contour-based form perception and exhibits a functional complexity analogous to mammalian extrastriate cortex.

Time course of simultaneous masking in the starling's auditory forebrain

Simultaneous masking of pure tones was studied in the primary auditory forebrain of a songbird species, the European starling (Sturnus vulgaris). The responses of 32 multi-unit clusters in the input layer of the auditory neostriatum (field L2a) were recorded via radiotelemetry from freely moving birds. The probe was a 10-ms tone burst at the units' characteristic-frequency (CF) presented 20 dB above the threshold. The masker was an 80-ms tone burst presented either at the units' CF (excitatory masker) or at a frequency located in inhibitory side-bands (inhibitory masker) of the units' tuning curves. The probe was presented either 3 ms or 63 ms after masker onset. Probes presented at a 3-ms delay were influenced at significantly lower levels of an excitatory masker than probes presented at a 63-ms delay. The mean difference in masker level at the detection thresholds for both probe delays was 8 dB. No difference in masker level was observed for inhibitory-frequency maskers. The observed neural masking effects may be explained by at least four mechanisms: (1) swamping of the probe response by the response to the masker, (2) a reduction of the probe response during neural adaptation of the response to the masker, (3) a reduction of the probe response during side-band inhibition in the central nervous system, and (4) suppression originating in the cochlea.

Adjustable frequency selectivity of auditory forebrain neurons recorded in a freely moving songbird via radiotelemetry

One of the hearing system's basic properties that determines the detection of signals is its frequency selectivity. In the natural environment, a songbird may achieve an improved detection ability if the neuronal filters of its auditory system could be sharpened to adapt to the spectrum of the background noise. To address this issue, we studied 35 multi-unit clusters in the input layer of the primary auditory forebrain of nine European starlings (Sturnus vulgaris). Microelectrodes were chronically implanted in this songbird's cortex analogue and the neuronal activity was transmitted from unrestrained birds via a miniature FM transmitter. Frequency tuning curves (FTCs) and inhibitory sidebands were determined by presenting a matrix of frequency-level combinations of pure tones. From each FTC, the characteristic frequency (CF) and several parameters describing the neurons' filter characteristics were derived and compared to the same recording site's filter function while simultaneously stimulating with a continuous CF tone 20 dB above the response threshold. Our results show a significant improvement of frequency selectivity during two-tone stimulation, indicating that spectral filtering in the starling's auditory forebrain depends on the acoustic background in which a signal is presented. Moreover, frequency selectivity was found to be a function of the time over which the stimulus persisted, since FTCs were much sharper and inhibitory sidebands were largely expanded several milliseconds after response onset. Neuronal filter bandwidths during two-tone stimulation in the auditory forebrain are in good agreement with psychoacoustically measured critical bandwidths in the same species. Radiotelemetry proved to be a powerful tool in studying neuronal activity in freely behaving birds.

A sensorineural progressive autosomal recessive form of isolated deafness, DFNB13, maps to chromosome 7q34-q36

Deafness is the most frequent sensorineural defect in children. The vast majority of the prelingual forms of isolated deafness are highly genetically heterogeneous with an autosomal recessive mode of inheritance. Using linkage analysis, we have mapped the gene responsible for a severe progressive sensorineural hearing loss, DFNB13, segregating in a large consanguineous family living in an isolated region in northern Lebanon. A maximum lod score of 4.5 was detected for markers D7S661-D7S498. Recombination events and homozygosity mapping by descent define a 17 cM gene interval in the chromosome region 7q34-q36, between the markers D7S2468/D7S2505, on the proximal side, and D7S2439, on the distal side.

Total prostate and transition zone volumes, and transition zone index are poorly correlated with objective measures of clinical benign prostatic hyperplasia

PURPOSE

We determined if total prostate volume, transition zone volume or transition zone index is correlated with the severity of clinical benign prostatic hyperplasia (BPH).

MATERIALS AND METHODS

A total of 93 men 52 to 85 years old, who were referred to a urology outpatient facility for treatment of clinical BPH, elevated serum prostate specific antigen or abnormal digital rectal examination, underwent measurement of total prostate and transition zone volume at transrectal ultrasonography. All men were requested to undergo uroflowmetry and complete the American Urological Association (AUA) symptom score.

RESULTS

The pairwise correlations between AUA symptom score, versus total prostate and transition zone volumes and transition zone index were not statistically or clinically significant. A weak pairwise relationship was observed between peak flow rate versus total prostate volume (r2 = 0.160), transition zone volume (r2 = 0.156) and transition zone index (r2 = 0.147). The pairwise relationships between AUA symptom scores versus all prostate volumes were not statistically significant for subjects with mild (score 8 or less) or moderate to severe (score more than 8) symptoms.

CONCLUSIONS

Total prostate and transition zone volumes, and transition zone index are not directly related to AUA symptom score and only weakly related to peak flow rate. These findings provide further evidence that the total prostate, total BPH and relative BPH volumes are not useful determinants of the severity of clinical BPH.

Effect of terazosin on prostatism in men with normal and abnormal peak urinary flow rates

OBJECTIVES

To determine if men with normal peak urinary flow rates (PFR) and prostatism respond to terazosin.

METHODS

Forty-one men over the age of 50 years with an American Urological Association (AUA) symptom score greater than 8, postvoid residual urine volume (PVR) less than 300 mL, and no clinical or biochemical evidence of prostate cancer were treated with terazosin independent of the baseline PFR. The effect of terazosin on the AUA symptom score and PFR were compared for subjects with a PFR of 15 mL/s or less (group I) and those with a PFR greater than 15 mL/s (group II).

RESULTS

The baseline age, AUA symptom score, prostate volume, and PVR were not significantly different between the two groups. The mean changes in AUA symptom score were -45.0% and -49.5% for groups I and II, respectively. The mean changes in PFR were 7.0% and -26.6% for groups I and II, respectively.

CONCLUSIONS

The effect of terazosin on AUA symptom score is independent of baseline PFR, indicating that the mechanism of action of terazosin is not exclusively mediated by reduction of bladder outlet obstruction. Randomized controlled studies are required to confirm this provocative observation.