Temporal encoding of two-dimensional patterns by single units in primate inferior temporal cortex. I. Response characteristics

We seek a general approach to determine what stimulus features visual neurons are sensitive to and how those features are represented by the neuron's responses. Because lesions of inferior temporal (IT) cortex interfere with a monkey's ability to perform pattern discrimination tasks we studied IT neurons. Previous single-unit studies have shown that IT neurons sometimes respond more strongly to complex stimuli (brushes, hands, faces) than to simple stimuli (bars, slits, edges). However, it is not known how specific stimulus parameters are represented by responses. We studied the responses of IT neurons in alert behaving monkeys to a large set of two-dimensional black and white patterns. The stimulus set was based on 64 Walsh functions that can be used to represent any picture with a resolution of one part in eight along each of two dimensions. The responses to these stimuli spanned a continuum from inhibition to strong excitation. A statistical test showed that the spike count was determined by which Walsh stimulus was presented. Hence, these stimuli form an adequate set for testing IT neurons. The responses showed temporal modulation of the spike train that could not be represented by a change in the spike count alone. Examples of this modulation were changes in latency, changes in the duration of the response, and alternating periods of excitation and inhibition. This temporal modulation may be important in representing stimulus parameters. The next paper in this series develops a method for quantifying this temporal modulation and shows that it is dependent on the stimulus. The third paper in this series shows that this temporal modulation contains more information about stimulus parameters than is contained in the spike count alone.     

Temporal encoding of two-dimensional patterns by single units in primate primary visual cortex. II. Information transmission

1. Previously, we studied how picture information was processed by neurons in inferior temporal cortex. We found that responses varying in both response strength and temporal waveform carried information about briefly flashed stationary black-and-white patterns. Now, we have applied that same paradigm to the study of striate cortical neurons. 2. In this approach the responses to a set of basic black and white pictures were quantified through use of a set of basic waveforms, the principal components (extracted from all the responses of each neuron). We found that the first principal component, which corresponds to the response strength, and others, which correspond to different basic temporal activity patterns, were significantly related to the stimuli, i.e., the stimulus drove both the response strength and its temporal pattern. 3. Our previous study had shown that, when information theory was used to quantify the stimulus-response relation, inferior temporal neurons convey over twice as much information in a response code that includes temporal modulation as in a response code that includes only the response strength. This study shows that striate cortical neurons also carry twice as much information in a temporal code as in a response strength code. Thus single visual neurons at both ends of a cortical processing chain for visual pattern use a multidimensional temporal code to carry stimulus-related information. 4. These results support our multiplex-filter hypothesis, which states that single visual system neurons can be regarded as several simultaneously active parallel channels, each of which conveys independent information about the stimulus.     

Cross-correlation of EMG reveals widespread synchronization of motor units during some slow movements in intact cats

It is commonly assumed that the motor units comprising a single mammalian muscle will be recruited asynchronously at subtetanic firing rates to produce smoothly modulated force output. However, electromyograms from certain neck muscles, recorded by implanted bipolar "patch" electrodes having large contacts, often exhibited a rhythmic clustering of spike activity whose patterns suggested that motor-unit firing was synchronized both within and across muscles. We have developed a computerized processing system that digitizes EMG activity and calculates auto- and cross-correlation products of selected segments. The presence or absence of synchronization caused by neural mechanisms can be identified and differentiated from that due to the rhythmicity of the behavior itself (e.g. shaking) or due to cross-talk, according to the shapes of the resultant correlograms. These methods have so far been applied to the study of hindlimb and neck muscle EMG during various natural motor behaviors, but they provide a general, quantitative tool for the study of an important aspect of motor control that may be overlooked by conventional sampling and smoothing techniques.     

The significance of incomplete excision in patients with basal cell carcinoma

Sixty-seven patients with incompletely excised basal cell carcinomas are reviewed. No recurrences were seen in seven patients who had immediate supplementary treatment; 23 of 60 patients submitted to a "wait and see" regimen developed recurrent disease, Recurrence was commoner in those in whom both the lateral and deep margins were involved, and when the incomplete excision was for recurrent disease. The latter recurrences were more difficult to control in patients who had previously had radiotherapy, when the deep margin was involved and when a flap had been used to close the resulting defect. A case is made for immediate re-excision for all patients with incompletely excised basal cell carcinomas.     

New Data on the Methohexital-Thiopental-Arrhythmia Issue

Previous reports of a much greater incidence of arrhythmias with thiopental anesthesia for electroconvulsive therapy (ECT) compared to methohexital were reexamined and the possible role of hypercapnia reconsidered. Review of 50 treatments with each agent in 13 patients who had received each at our facility revealed only one brief episode of arrhythmia. The importance of postictal hyperventilation in preventing hypercapnia and associated arrhythmias was suggested.     

Is sexual abuse in childhood or adolescence a predisposing factor for HIV infection during adolescence?

This exploratory study was conducted to determine whether sexual abuse might be a risk factor or marker for other risk factors for Human Immunodeficiency Virus (HIV) infection. Twenty-five HIV-positive adolescents were assessed for a variety of possible risk factors for HIV infection, including prior history of sexual abuse. Fifteen (60%) had a history of sexual abuse. A history of sexual abuse may be a risk factor for HIV infection directly, or it may be associated with or predispose one to other risk factors. The latter mechanism may be related to the long-term negative outcomes of some individuals with a history of sexual abuse. These may include same-sex sexual experiences as an adolescent, re-victimization with additional episodes of abuse, multiple consensual sexual partners, and drug and/or alcohol abuse. Preventive interventions aimed at reducing the risk of HIV infection must take a history of sexual abuse into account. Patients with such a history deserve intensive psychological counseling to help prevent adverse behavioral outcomes that can result in HIV infection.     

Area postrema and the anorectic actions of dexfenfluramine and amylin

The present study examined whether the area postrema and adjacent nucleus of the solitary tract (AP/NTS) is necessary for the expression of anorexia to two classes of anorectic agent. The first agent is the serotonergic agonist, dexfenfluramine (DFEN) and the second is the pancreatic peptide, amylin. Rats were prepared with either aspiration lesions of the AP/NTS or a sham operation. Rats with such lesions (APX) displayed normal anorexia following administration of DFEN, but the anorectic effect of amylin was completely eliminated. The magnitude of a conditioned flavor aversion to DEN was similar in APX and sham operated controls but, unlike controls, APX rats did not reduce total intake in the two-bottle preference test. Finally, the induction of Fos-like immunoreactivity (Fos-ir) following either DFEN or amylin was examined in both APX and sham operated groups. Both agents induced Fos-ir in the AP and/or NTS of sham operated rats, and this region was entirely absent in the APX rats. DFEN-induced Fos-ir was reduced greatly in the PVN of APX rats, but appeared normal in several other regions surveyed, including the central nucleus of the amygdala and the dorsal striatum. In contrast, amylin-induced Fos-ir was reduced in many rostral brain regions of APX rats. These data indicate that neither the anorexia nor the flavor aversion that are produced by DFEN are dependent upon the AP, and in particular that Fos-ir induced by DFEN in the LPBE is not due to afferents from the AP/NTS. In contrast, the anorectic effect of amylin seems to be due principally to its direct action at the AP/NTS.     

Immunogenicity and reactogenicity in UK infants of a novel meningococcal vesicle vaccine containing multiple class 1 (PorA) outer membrane proteins.

The development of effective vaccines against serogroup B meningococci is of great public health importance. We assessed a novel genetically engineered vaccine containing six meningococcal class 1 (PorA) outer membrane proteins representing 80% of prevalent strains in the UK. 103 infants were given the meningococcal vaccine at ages 2, 3 and 4 months with routine infant immunisations, with a fourth dose at 12-18 months. The vaccine was well tolerated. Three doses evoked good immune responses to two of six meningococcal strains expressing PorA proteins contained in the vaccine. Following a fourth dose, larger bactericidal responses to all six strains were observed, suggesting that the initial course had primed memory lymphocytes and revaccination stimulated a booster response. This hexavalent PorA meningococcal vaccine was safe and evoked encouraging immune responses in infants. Vaccines of this type warrant further development and evaluation.     

Secondary prevention of excessive alcohol use: assessing the prospects of implementation

BACKGROUND: Alcohol risk and harm reduction is a public health approachthat goes beyond specialized treatments for alcoholism. Thegreatest potential for reducing alcohol risk and harm in a populationdepends on the extent to which health care practitioners usesecondary prevention programmes. OBJECTIVE: We aim to assess the factors that affect the prospects of disseminatingcomprehensive, secondary prevention programmes into mainstreampractice. METHOD: A decision balance was used to assess the prospects of practitionersimplementing comprehensive programmes systematically. The stages-of-changemodel provides perspectives about behaviour change with regardto patients, practitioners and practice settings. RESULTS AND CONCLUSIONS: Programme implementation is extremely unlikely given the currentorganization of health care settings. To maintain the use ofsuch programmes, we need to change the "unit of leverage" inthe system: from the clinical encounter—that is, practitionersworking with individual patients in a case-finding manner—toan organizational level—that is, the appropriate use ofmanagerial and information systems supporting health care settingsto identify at-risk patients systematically as they enter primarycare and hospital settings. With appropriate infrastructuresupport, practitioners will be able to fulfil the potentialfor as well as maintain the use of comprehensive, secondaryprevention programmes to reduce alcohol risk and harm in thepopulation. Keywords. Alcohol abuse, general practice, implementation, secondary prevention.     

Programmes for tobacco and alcohol users in Australian work-places

This article presents findings from a survey of programmes available for tobacco and alcohol users working in 455 of Australia's top 600 companies. Companies were twice as likely to have programmes for smokers (43%) as for problem drinkers (24%) and these programmes were more apparent in large companies. The majority of programmes for smoking were delivered within a health promotion context which included other life-style issues, such as nutrition, exercise, weight management and stress management. Although Employee Assistance Programs (EAPs) were the most commonly available type of work-place programme for excessive drinkers and other drug users, followed by Alcoholics Anonymous and local hospital clinics, only 6% had an EAP for alcohol. Only 21% of programmes for smokers and 12% for excessive alcohol users were evaluated. Around one-quarter of companies knew the costs of smoking programmes, and 9% reported costs of conducting programmes for excessive alcohol consumers.