Visual N1

The visual N1 is a visual evoked potential, a type of event-related electrical potential (ERP), that is produced in the brain and recorded on the scalp. The N1 is so named to reflect the polarity and typical timing of the component. The "N" indicates that the polarity of the component is negative with respect to an average mastoid reference. The "1" originally indicated that it was the first negative-going component, but it now better indexes the typical peak of this component, which is around 150 to 200 milliseconds post-stimulus. The N1 deflection may be detected at most recording sites, including the occipital, parietal, central, and frontal electrode sites. Although, the visual N1 is widely distributed over the entire scalp, it peaks earlier over frontal than posterior regions of the scalp, suggestive of distinct neural and/or cognitive correlates. The N1 is elicited by visual stimuli, and is part of the visual evoked potential – a series of voltage deflections observed in response to visual onsets, offsets, and changes. Both the right and left hemispheres generate an N1, but the laterality of the N1 depends on whether a stimulus is presented centrally, laterally, or bilaterally. When a stimulus is presented centrally, the N1 is bilateral. When presented laterally, the N1 is larger, earlier, and contralateral to the visual field of the stimulus. When two visual stimuli are presented, one in each visual field, the N1 is bilateral. In the latter case, the N1’s asymmetrical skewedness is modulated by attention. Additionally, its amplitude is influenced by selective attention, and thus it has been used to study a variety of attentional processes.

Visual system

The visual system is the part of the central nervous system which gives organisms the ability to process visual detail, as well as enabling the formation of several non-image photo response functions. It detects and interprets information from visible light to build a representation of the surrounding environment. The visual system carries out a number of complex tasks, including the reception of light and the formation of monocular representations; the buildup of a nuclear binocular perception from a pair of two dimensional projections; the identification and categorization of visual objects; assessing distances to and between objects; and guiding body movements in relation to the objects seen. The psychological process of visual information is known as visual perception, a lack of which is called blindness. Non-image forming visual functions, independent of visual perception, include the pupillary light reflex (PLR) and circadian photoentrainment.

Structure

This article mostly describes the visual system of mammals, humans in particular, although other "higher" animals have similar visual systems (see bird vision, vision in fish, mollusc eye, reptile vision). In the case of mammals (including humans), the visual system consists of:

Visual (album)

Visual is the third studio album produced by the Dominican based electronic rock band Tabu Tek. This second production was released on the year 2003 in Santo Domingo, Dominican Republic. The fourth song of the album, Compadre Pedro Juan, is a rock tribute to Luis Alberti, father of merengue music. The song was previously set to be released in the merengue tribute Rockero Hasta La Tambora made by Dominican rock bands. The album is distinguished by the more rock based sound with less of the electronica aspect found in their previous production Girar. Nevertheless, it was well received and played in rock stations around the country.

Track listing

Visual 1050

The Visual 1050 was an 8-bit desktop computer sold by Visual Technology in the early 1980s. The computer ran under the CP/M operating system and used 2 400KB, 5¼, SSDD, 96tpi floppy disk drives (TEAC FD-55E) for mass storage with an optional 10Mb external Winchester hard disk drive. In addition to the Zilog Z80 processor clocked at 4 MHz, the Visual 1050 also included a MOS Technology 6502 used as a graphics coprocessor.

Overview

The Visual 1050 featured a dual-processor architecture; Z80A processor as the main CPU and a 6502 to drive the display.

Memory: 160K of RAM was included with the system. 128K of this was programmable and 32K reserved for use by the display processor.

Screen: The display unit was 640×300 pixel, 80×25 character (8×12 dot matrix) green monochrome CRT bit-mapped display. The display offered programmable features which could be invoked from the main processing unit via a character-stream interface built in between the Z80 CPU and 6502 co-processor.

Communication ports An RS-232C serial port and Centronics parallel port.