Sensitivity of neurons in cat primary auditory cortex to tones and frequency-modulated stimuli. I: Effects of variation of stimulus parameters.
ABSTRACT In the primary auditory cortex (AI) of barbiturate-anesthetized cats multi-unit responses to tones and to frequency-modulated (FM) tonal stimuli were analyzed. Characteristic frequency (CF), sharpness of tuning, minimum threshold, and dynamic range of spike count--intensity functions were determined. Minimum threshold and dynamic range were positively correlated. The response functions to unidirectional FM sweeps of varying linear rate of change of frequency (RCF) that traversed the excitatory frequency response areas (FRAs) displayed a variety of shapes. Preferences for fast RCFs (> 1000 kHz/s) were most common. Best RCF was not correlated with measures of sharpness of tuning. Directional preference and sensitivity were quantified by a DS index which varied with RCF. About two-thirds of the multi-unit responses showed a preference for downward sweeps. Directional sensitivity was independent of CF and independent of best RCF. Measurements of latencies of phasic responses to unidirectional FM sweeps of different RCF demonstrated that the discharges of a given multi-unit over its effective RCF range were initiated at the same instantaneous frequency (effective Fi), independent of RCF. Effective Fis fell within the excitatory FRA of a given multi-unit. The relationships of effective Fis to CF show that responses were evoked only when the frequency of the signal was modulated towards CF and not when modulated away from it, and that responses were initiated before the modulation reached CF. Changes in the range and depth of modulation had only minor, if any, effects on RCF response characteristics, FM directional sensitivity, and effective Fis, as long as the beginning and ending frequencies of FM sweeps fell outside a multi-unit's FRA. Stimulus intensity also had only moderate effects on RCF response characteristics and DS. However, effective Fis were influenced in systematic fashions; with increases in intensity, effective Fis to upward and downward sweeps decreased and increased, respectively. Thus, for higher intensities FM responses were initiated at instantaneous frequencies occurring earlier in the signal. The results are compared with previous data on tone and FM sensitivity of auditory neurons in cortical and subcortical structures, and mechanisms of FM rate and directional sensitivity are discussed. The topographic representations of these neuronal properties in AI are reported in the companion report.
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ABSTRACT: Introduction: It is a common view that different mental illnesses are widely associated with dangerous, threat-posing behavior and law-breaking . The traits of this common belief can be found in both popular novels and numerous movies . This tendency contributes to perpetuating the stigmatisation of the psychiatric patients among lay people. Unfortunately, there do not seem to be enough data to prove the authors of the above-mentioned ﬁlms and novels wrong. Aims: The paper analyzes the problem of law-breaking by the mentally disordered in order to establish the frequency of violent and dangerous behaviors in this patient group. The data collected is compared to other existing data regarding this problem. Methods: We carried out an analysis of cases, held from 2007 to 2009 in Katowice, Silesia Region, Poland, concerning compulsory psychiatric treatment or conﬁnement in a medical institution on the grounds of mental incompetence to commit an offence or mental unﬁtness to stand the trial. The cases records were obtained from both the court and the public prosecutor’s ofﬁce. Simultaneously, the analysis of other available data from abroad and corresponding publications was conducted. Results: As a result of thorough analysis of court’s and prosecutor’s case records, 14 cases out of around 5000 were found to meet the research criteria. In all cases, the offenders were male, their mean age was 44.6 years. As a result of committing an offense, all the offenders were diagnosed by psychiatrists in the course of their trials. Most of the offenders were diagnosed with schizophrenia (n = 10 cases). Other diagnoses established included paranoid personality disorder (n = 1), bipolar affective disorder with manic episode (n = 1), schizoaffective disorder (n = 1) and delusional disorder (n = 1). 9 out of 14 offenders were diagnosed prior to the offence, some of whom were also hospitalized (n = 5). 8 of analyzed cases concerned use of violence, 3 concerned larceny, 2 concerned posing a threat to others’ life or health and 1 concerned fraud. 2 of the offenders were previously sentenced for other offenses. By court’s verdict, 12 of the offenders were compulsory treated in psychiatric institution, 10 out of whom is still hospitalized. This results seem to conﬁrm the outcomes of other research, conducted by Janofsky et al., which also showed that it is only in a very small number of criminal cases held in the local court that the mentally disordered offenders could be found to be involved . Conclusions: The small number of cases meeting the criteria of the research (14 cases in the whole of 5000) suggests that mentally disordered persons do not break law often. There seems to be a higher risk associated with male gender, though. Also, the frequency of violent acts and offences committed despite previous treatment is disturbing. References  Filipovits, D., Farkas, M., Violent behaviour and stigmatisation among psychiatric patients. Psychiatr Hung.2008.  Damjanovic, A., Vukovic, O., Psychiatry and movies. Psychiatr Danub.2009.  Janofsky, J.S., Dunn, M.H., Roskes, E.J., Briskin, J.K., Rudolph, M.S., Insanity defense pleas in Baltimore City: an analysis of outcome. Am J Psychiatry. 1996.European Neuropsychopharmacology 09/2011; 21. · 5.40 Impact Factor
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ABSTRACT: The mismatch negativity (MMN) is a pre-attentive auditory event-related potential (ERP) component that is elicited by a change in a repetitive acoustic pattern. It is obtained by subtracting responses evoked by frequent 'standard' sounds from responses evoked by infrequent 'deviant' sounds that differ from the standards along some acoustic dimension, e.g., frequency, intensity, or duration, or abstract feature. The MMN has been attributed to neural generators within the temporal and frontal lobes. The mechanisms and meaning of the MMN continue to be debated. Two dominant explanations for the MMN have been proposed. According to the "neural adaptation" hypothesis, repeated presentation of the standards results in adapted (i.e., attenuated) responses of feature-selective neurons in auditory cortex. Rare deviant sounds activate neurons that are less adapted than those stimulated by the frequent standard sounds, and thus elicit a larger 'obligatory' response, which yields the MMN following the subtraction procedure. In contrast, according to the "sensory memory" hypothesis, the MMN is a 'novel' (non-obligatory) ERP component that reflects a deviation between properties of an incoming sound and those of a neural 'memory trace' established by the preceding standard sounds. Here, we provide a selective review of studies which are relevant to the controversy between proponents of these two interpretations of the MMN. We also present preliminary neurophysiological data from monkey auditory cortex with potential implications for the debate. We conclude that the mechanisms and meaning of the MMN are still unresolved and offer remarks on how to make progress on these important issues.Brain Topography 11/2013; · 2.52 Impact Factor
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ABSTRACT: The functional properties of auditory cortex neurons are most often investigated separately, through spectrotemporal receptive fields (STRFs) for the frequency tuning and the use of frequency sweeps sounds for selectivity to velocity and direction. In fact, auditory neurons are sensitive to a multidimensional space of acoustic parameters where spectral, temporal and spatial dimensions interact. We designed a multi-parameter stimulus, the random double sweep (RDS), composed of two uncorrelated random sweeps, which gives an easy, fast and simultaneous access to frequency tuning as well as frequency modulation sweep direction and velocity selectivity, frequency interactions and temporal properties of neurons. Reverse correlation techniques applied to recordings from the primary auditory cortex of guinea pigs and rats in response to RDS stimulation revealed the variety of temporal dynamics of acoustic patterns evoking an enhanced or suppressed firing rate. Group results on these two species revealed less frequent suppression areas in frequency tuning STRFs, the absence of downward sweep selectivity, and lower phase locking abilities in the auditory cortex of rats compared to guinea pigs.Brain Topography 05/2014; · 2.52 Impact Factor