Presaccadic Spike Potential Research Articles

Neural correlates of attentional orienting with neutral and fearful gaze cues in 12-month-olds

ABSTRACT Infants use information on gaze direction and facial expressions for social referencing when encountering various objects in their environment. However, it remains unclear how these social cues influence attentional orienting in infants. Using event-related potentials (ERPs), we investigated the neural correlates of attentional orienting cued by an averted gaze with neutral and fearful expressions in 12-month-olds. We focused on the ERPs in response to a face (N290, P400, and Nc) as well as a saccade toward the target (the presaccadic spike potential: SP) and found that the amplitudes of the face-sensitive ERPs (N290 and P400) were larger for directed than averted gaze direction irrespective of facial expression. Furthermore, the amplitude of the SP involved in overt orienting was larger for fearful expressions than for neutral expressions, irrespective of gaze congruency. These results suggest that information on gaze direction and facial expression, specifically neutral and fearful expressions, may be processed independently, and that fearful expressions dominantly influence the neural correlates of attentional orienting in infants around 12 months of age.

The coincidence between late non-phase-locked gamma synchronization response and saccadic eye movements

The event-related response in the gamma (30–45 Hz) frequency band was studied in healthy subjects ( n=45) viewing sequentially presented pictures from the International Affective Picture System. The distinct non-phase-locked gamma response was obtained in characteristic time window (200–400 ms) with clear-cut centro-parietal location. The strong coincidence between induced gamma oscillations and saccadic eye movements was revealed. We suggest that saccade-related gamma increase is another manifestation of the phenomenon known as presaccadic spike potential, which is commonly registered over parietal scalp leads at 10–20 ms prior to saccade onset. It is hypothesized that late non-phase-locked gamma synchronization mainly reflects activity of a system responsible for attentional tuning and motor planning/execution of saccadic eye movements.

The effects of time point alignment on the amplitude of averaged orbital presaccadic spike potential (SP)

Effects of two time-point selection averaging techniques on orbital SP amplitude were studied on 10 normal subjects performing horizontal saccades. One technique involved averaging from the SP peak, another technique involved averaging from the saccadic onset. The time-point selection methods only affected the magnitude of SP amplitude but did not interact with experimental conditions. Repeated measures analysis of variance showed that SP amplitudes were higher in data aligned on SP peak than those aligned on saccadic onset ( P < 0.01). No significant second order (saccade by degree) or third order (saccade by direction) interactions involving averaging method were found ( P>0.05).

A frontal cortical potential associated with saccades in humans.

We describe a frontal EEG potential which begins 25-35 ms before intentional saccadic eye movement. It consists of a 15-20 muvolt monophasic positive waveform with peak during or just after movement, and returns to EEG baseline 150-200 ms after its onset. The waveform is largest at a midline position just anterior to FZ (10-20 system), is independent of visual input such as fixation guides, and is not related to saccade direction or amplitude. The potential is difficult to observe in some subjects and is independent of the "pre-saccadic spike potential". It may be related to the discharge of single cortical neurons that signal the initiation of saccadic movements, but not their exact metrics; a possible generator is the supplementary eye fields of the dorsomedial prefrontal cortex.

Directional tuning of the human presaccadic spike potential

This study examined the behavior of the presaccadic spike potential (SP) in 20 normal, right-handed subjects for self-paced 10° saccades along vertical, horizontal and oblique meridians. The SP was recorded differentially between posterior parietal sites and a linked ear reference. The SP amplitude showed clear directional tuning properties, with the maximum response prior to saccades directed in an oblique, downward and contralateral direction. The minimum response was obtained for upward saccades. The data were fitted to a model consisting of 3 components: (1) a constant component reflecting saccadic amplitude; (2) a component with narrow directional tuning that is modeled from properties of frontal eye field neurons in monkeys; and (3) a component with broad directional tuning that is designed to reflect directional tuning properties of potentials originating from horizontal and vertical saccade generators, motoneurons and extraocular muscles. The narrowly tuned mechanism is sufficient to encode the direction of saccades. One surprising finding, though, was that the broadly tuned mechanism was necessary and sufficient to account for differences in SP amplitude as a function of electrode laterality. Application of this model approach to published data for periorbital SP, recorded between periorbital and parietal sites (G.W. Thickbroom and F.L. Mastaglia, Electroencephalogr. Clin. Neurophysiol., 64 (1986) 211–214), suggested that this potential represents a broadly tuned mechanism with directional tuning opposite the parietal SP. These data indicate that the periorbital and parietal SPs represent activation of different networks of central generators.

Presaccadic spike potential with vertical saccades

Presaccadic spike potentials were recorded from four electrodes placed around the eyes for 20 degree vertical saccadic eye movements. Twenty upward and 20 downward saccades were recorded using electro-oculography and the spike potentials back-averaged from the start of the eye movement. Separate average waveforms were obtained for upward and downward saccades. The onset of the spike was between 17.3 and 6.8 ms before the start of the saccade with downward saccades having earlier onsets than upward saccades. This difference was only significant in the right eye (P less than 0.025). The peak occurred between 3.4 ms before to 5.2 ms after the start of the eye movement and was earlier with downward saccades. This was only significant in the right eye (P less than 0.025). The onset to peak amplitude measured between 15.9 and 42.3 microV with no statistical difference between upward and downward saccades. It was found, however, that the electrodes placed below the eyes recorded larger amplitudes for upward saccades than the other electrode-recording positions (right eye P less than 0.05, left eye P less than 0.025). A second component to the spike potential waveform was observed in many of the recordings and a possible origin of this component due to eyelid activity is hypothesized.

Changes in the presaccadic spike potential with age

Presaccadic spike potentials were recorded from an electrode below the eye to 20° horizontal saccades in 2 groups of 10 subjects; a young group with a mean age of 26 years and an old group with a mean age of 77 years. The onset and peak latencies, relative to the beginning of the eye movement, and the onset-peak amplitudes were measured for abduction and adduction movements separately. There was no significant difference in the onset or peak latencies of the 2 groups with either abduction or adduction. The amplitude, however, was significantly greater in the young group with both abduction ( P < 0.01) and adduction ( P < 0.025). Possible explanations of these results are given and the implications of the findings on the investigation of presaccadic spike potentials in both normal and pathological subject groups are discussed.

Presaccadic spike potential with congenital lateral rectus palsy

Presaccadic spike potentials were recorded with 20° horizontal eye movements in a subject with a congenital left lateral rectus palsy. Electrodes at the inner and outer canthi recorded the eye movements and an electrode below the eye recorded the presaccadic spikes. The responses to 20 abducting and 20 adducting saccades were back-averaged from the onset of the eye movement with the wave forms for abduction and adduction averaged separately. Recordings were made from each eye under 2 conditions: firstly with the eye from which the spikes were being recorded fixating and secondly with the eye from which the spikes were not being recorded fixating. In each case the non-fixating eye was occluded throughout. Recordings were made with eye position monitored initially in the eye from which the spikes were recorded and repeated with eye position monitored in the other eye. Results show that spikes could be recorded during abduction and adduction movements of both eyes but only if eye position was monitored in the right eye. Using the left eye as position monitor gave very broad low amplitude spikes. When eye position was monitored in the right eye the spikes recorded during abduction of the left eye had a low amplitude compared to those recorded during right eye abduction; right eye adduction spikes were also of low amplitude. A possible explanation for these findings and their implications on future recordings in pathological cases are discussed.

Presaccadic spike potential to horizontal eye movements

Presaccadic spike potentials prior to 20 ° horizontal eye movements were recorded from 4 electrode sites around the eye with Pz as reference. The technique of back-averaging from the onset of the saccade was used and separate wave forms were obtained for abducting and adducting movements. The spike onset began between 12.0 and 4.4 msec before the beginning of the saccade with a significantly earlier onset with adduction (right eye P < 0.001, left eye P < 0.025). The peak occurred between the onset of eye movement and 7.8 msec after the beginning of the movement; the peak also occurred significantly earlier with adduction (right eye P < 0.01, left eye P < 0.01). The amplitude of onset to peak measured from 32.2 to 47.0 μV with greater amplitudes on adduction compared to abduction although the differences were not statistically significant. Several of the traces also showed a later smaller component, after the main onset-to-peak complex, that has not been previously reported.

On the origin of the presaccadic spike potential

The spike potential (SP) accompanying the onset of saccadic eye movements has been reported to originate near the orbital region. Its dependence on saccade size, however, does not correlate with the behaviour of any of the possible sources of the potential available in the orbital region. The exact size dependence cannot be studied fro results obtained with classical ENG methods to detect the saccadic onset and furthermore without removal of the artefact in the signal caused by the corneo-retinal potential. We recorded the SP by monitoring the eye movements with an infrared scleral reflection method (IRIS), and carefully studied the SP amplitude as a function of saccade size, and revealed a more realistic function. Furthermore, removal of the artefact of the corneo-retinal potential revealed a biphasic wave shape of the SP instead of the usually observed monophasic peak. These results support the hypothesis that this electrical activity accompanying the onset of saccadic eye movements originates in the oculomotor neurones innervating the ocular muscle units.

Presaccadic spike potential: a computer model based upon motor unit recruitment patterns in the extraocular muscles

Details are presented of a computer model of the presaccadic ‘spike’ potential based upon the discharge properties of motor units in the extraocular muscles. The model provides support for the hypothesis that the spike potential represents the summated electrical activity from the near-synchronous recruitment of motor units in the extraocular muscles by the presaccadic burst of motoneurone activity.

Presaccadic spike potential. Relation to eye movement direction

The spike potential (SP) which precedes horizontal saccadic eye movement has been shown to arise in the agonist lateral and medial rectus muscles of the two eyes. To determine whether other extra-ocular muscles also generate an SP, recordings were carried out in normal subjects performing vertical and oblique as well as horizontal saccades. An SP was recorded before saccades in all directions. The potential was highest in amplitude with horizontal or oblique abducting saccades and was higher in amplitude with vertical upgoing than downgoing saccades.

The human pre-saccadic spike potential: Influences of a visual target, saccade direction, electrode laterality and instructions to perform saccades

Three components of pre-saccadic evoked potentials have been identified in humans: a slow negative shift (SNS), a positive antecedent potential (AP) and a spike potential (SP). This study examined the influences of: (1) instructions to the subject to make saccades; (2) the presence of a visual target: and (3) the direction of the saccades on the amplitude of the averaged SP, which was recorded from P 3 and P 4 (International 10/20 System) in 20 normal, right-handed subjects. Recordings were made for spontaneous saccades prior to receiving instructions in six subjects. Twenty subjects performed self-paced saccades in the presence of a 10° visual target (two red LEDs) and while blindfolded in a dark room. The SP was either absent or grossly altered (broadened) for spontaneous saccades in an illuminated room; it was robust for self-paced saccades in light or darkness. Three-way analysis of variance revealed a highly significant cortical laterality (P 3 vs P 4) × saccade direction interaction ( P < 0.001), relecting that for a given saccade direction, the SP was larger over the contralateral recording site for the self-paced light (SPL) paradigm (Newman-Keuls test). In the self-paced dark (SPD) paradigm, though, this was only true for saccades to the right. By contrast, scatter plots of the directional indices (D.I.= [(SP for collateral) ± (SP for ipsilateral)]/[SP for contalateral) + (SP for ipsilateral saccades)] for left (P 3) and right (P 4) recording sites from individual subjects revealed a significant negative correlation for both SPL ( r = 0.74) paradigms. This implies that the SP for an individual subject tends to be larger at P 3 and P 4 for saccades in one direction rather than for contralateral saccades. Thus, instructions to perform saccades, saccade direction and left vs right electrode sites all affect the pre-saccadic SP in humans.

Pre-motor negativity (PMN) associated with unpredictably triggered eye and finger movement in man

This study examined the behavior of the presaccadic spike potential (SP) in 20 normal, right-handed subjects for self-paced 10° saccades along vertical, horizontal and oblique meridians. The SP was recorded differentially between posterior parietal sites and a linked ear reference. The SP amplitude showed clear directional tuning properties, with the maximum response prior to saccades directed in an oblique, downward and contralateral direction. The minimum response was obtained for upward saccades. The data were fitted to a model consisting of 3 components: (1) a constant component reflecting saccadic amplitude; (2) a component with narrow directional tuning that is modeled from properties of frontal eye field neurons in monkeys; and (3) a component with broad directional tuning that is designed to reflect directional tuning properties of potentials originating from horizontal and vertical saccade generators, motoneurons and extraocular muscles. The narrowly tuned mechanism is sufficient to encode the direction of saccades. One surprising finding, though, was that the broadly tuned mechanism was necessary and sufficient to account for differences in SP amplitude as a function of electrode laterality. Application of this model approach to published data for periorbital SP, recorded between periorbital and parietal sites (G.W. Thickbroom and F.L. Mastaglia,Electroencephalogr. Clin. Neurophysiol., 64 (1986) 211–214), suggested that this potential represents a broadly tuned mechanism with directional tuning opposite the parietal SP. These data indicate that the periorbital and parietal SPs represent activation of different networks of central generators.

Changes in cortical short latency somatosensory evoked potentials with stimulus frequency and interfering stimulation

This study examined the behavior of the presaccadic spike potential (SP) in 20 normal, right-handed subjects for self-paced 10° saccades along vertical, horizontal and oblique meridians. The SP was recorded differentially between posterior parietal sites and a linked ear reference. The SP amplitude showed clear directional tuning properties, with the maximum response prior to saccades directed in an oblique, downward and contralateral direction. The minimum response was obtained for upward saccades. The data were fitted to a model consisting of 3 components: (1) a constant component reflecting saccadic amplitude; (2) a component with narrow directional tuning that is modeled from properties of frontal eye field neurons in monkeys; and (3) a component with broad directional tuning that is designed to reflect directional tuning properties of potentials originating from horizontal and vertical saccade generators, motoneurons and extraocular muscles. The narrowly tuned mechanism is sufficient to encode the direction of saccades. One surprising finding, though, was that the broadly tuned mechanism was necessary and sufficient to account for differences in SP amplitude as a function of electrode laterality. Application of this model approach to published data for periorbital SP, recorded between periorbital and parietal sites (G.W. Thickbroom and F.L. Mastaglia,Electroencephalogr. Clin. Neurophysiol., 64 (1986) 211–214), suggested that this potential represents a broadly tuned mechanism with directional tuning opposite the parietal SP. These data indicate that the periorbital and parietal SPs represent activation of different networks of central generators.