Effects of Aging on Visual Evoked Gastone G. Celesia, MD, Richard F.
Daly,
Responses
MD
\s=b\ The effects of aging on visual evoked responses (VER) and critical frequency of photic driving (CFPD) was studied in 74 volunteers aged 18 to 79. The amplitude of VER to pattern reversal stimulation did not vary with sex or age. The latencies of the first major negative and of the first major positive deflection of the VER were significantly delayed (P < .001) with advancing age. This increase of latency probably reflects a slowing of conduction velocity in the optic nerve or optic pathways or both. CFPD, defined as the highest frequency of photic driving response expressed in flashes per second, showed an inverse correlation, decreasing with age in older subjects. Critical frequency of photic driving is the electrophysiological counterpart of critical flicker fusion, which is known to decrease with advancing age. These data support the concept that aging influences the functions of specialized sensory
systems. (Arch Neurol 34:403-407, 1977)
utilized: 02-A2; Ol-Al; Oz-Al; Oz-A2; 02-P4; 01-P3; Oz-Pz; and Oz-Cz. The input from the electrodes was fed into four preamplifi¬ ers adjusted to a bandwidth of 0.3 Hz to 1 kHz. The output was fed simultaneously into an averager and an oscilloscope. Writeouts from the averager were made with an X-Y plotter. The subject was comfortably seated on
the
electroencephalogram recording chair
1 m from a translucent screen on which the pattern was projected from the rear. A visual generated a checkerboard patterned stimulus in which dark and bright squares rhythmically exchanged their positions. The whole stimulating field subtended an angle of 9.3° with each indi¬ vidual check of the checkerboard subtend-
Fig 1.—Pattern reversal evoked responses in two left (OS) eyes. LD indicates latency difference latency in milliseconds of wave P1.
controls (A and B) from right (OD) and for wave P1. Numbers indicate peak
OD
is known that the conduction
It velocity of peripheral grad¬ advancing age.1·2 ually decreases nerves
with This phenomenon is attributed to a loss of large fibers and/or to segmen¬ tal demyelination of some axons.3·4 Central nervous system pathways may be similarly affected by the aging process. To test this possibility, visual evoked responses (VER) and critical frequency of photic driving (CFPD) were studied in 74 volunteers aged 18 to 79.
92.8
96.2
OS
METHOD Silver-silver chloride electrodes were applied to the scalp with collodion according to the 10-20 International System. Electrode impedance was below 5,000 . The following montages were
Accepted for publication Feb 23, 1977. From the Department of Neurology, St Louis University and the Veterans Administration Hospital (Dr Celesia); and the Department of Neurology, University of Wisconsin Center for Health Sciences, Madison (Dr Daly). Reprint requests to Department of Neurology, St Louis University, 1221 S Grand Blvd, St Louis, MO 63104 (Dr Celesia).
Downloaded From: http://archneur.jamanetwork.com/ by a University of Pennsylvania User on 06/19/2015
96.4
5 +
LD
:
0.2
µ
ing 15.5 minutes of arc measured at the subject's eye. The luminance of the pattern
stimulation was 10 foot-lamberts. Stimulation was carried out in a partially darkened room with background lumi¬ nance of 0.01 foot-lamberts. Subjects were instructed to remain still and fixate on a black dot at the center of the screen. Flashes were generated by a photic stimu¬ lator set at intensity "1." A stroboscope was placed 45 cm in front of the subject's eye. Stimulation began at a low frequency of flashes and was gradually increased until no photic driving could be obtained. The increments in the frequency of flashes
Visual Evoked Responses to Pattern Reversal Checks of 15.5' Subtense Peak Latencies Peak Latency,
Stimulation of Right Eye
Electrode N1
02-P4
N1
P1
01-P3
Mean 73.7
Range
Position Oz-Pz
N1 P1
67.2-89.6 89.6-116.8 67.2-89.6 92-116.8 67.2-89.6 92-116.8
100.9 73.8 100.1
73.8 100.1
msec
Stimulation of Left
Range 68.8-87.2 90.4-116 68.8-87.2 89.6-116 68.8-87.2 89.6-116
Eye
Mean 73.7 99.3 73.5 98.9 73.9
~99
stepwise as follows: 15, 20, 25, 31, 40, 50, 62, 76, 85, 90,100. Two hundred fifty-six
were
samples were averaged over 204.8 msec immediately following the pattern reversal or a flash. Only for flash stimulation equal or
above 50 flashes per second were 512 further improve the
samples summated to signal to noise ratio.
Pattern stimulation always preceded flash stimulation. Pattern stimulation was carried out with natural pupils, while flash stimulation was undertaken after the pupils were dilated with synephrine 2.5% solution. Monocular stimulation was used. Every volunteer had normal findings on neurological and ophthalmological exami¬ nation and agreed to participate in the study with full knowledge of the exper¬ imental nature of the research.
RESULTS The ages of the 74 volunteers ranged from 18 to 79 years, with a mean of 38.4 and a median of 31 years. There were 40 women and 34 men. Sixteen subjects wore corrective lenses during testing, but did not require more than +1.5 diopter cor¬ rection to achieve 20/20 visual acuity. The remainder had normal visual acuity without corrective lenses. Evoked responses to pattern rever¬ sal consisted of a major negative wave (Nl) with a mean peak latency of 73.7 msec followed by a major positive wave (PI) with a mean peak latency of 97.8 msec (Fig 1). Wave Nl was occa¬ sionally preceded by a small positive wave.
Referential and bipolar recordings compared in 20 volunteers. The amplitude of VERs from 02-A2, 01-A1, and Oz-Cz was larger than VERs from 02-P4, 01-P3, and Oz-Pz, but quite similar to responses obtained from OzCz. Muscle contamination was a frequent problem in referential re¬
were
cordings; therefore,
we
arbitrarily
limited our study to bipolar record¬ ings. No significant differences were seen in the peak latencies of the VERs
AGE
IN YEARS
Fig 2.—Peak latency distribution of wave N1 in relation to age. Lower line is regression line; upper line is limit of normal set at 2.5 times standard deviation of regression line. Numbers indicate value occurring repeatedly at same point on
graph.
Downloaded From: http://archneur.jamanetwork.com/ by a University of Pennsylvania User on 06/19/2015
among the midline and lateral
occip¬ ital recordings (Table). Also, the peak
latencies of VERs obtained with stim¬ ulation of the right eye were similar to those obtained with stimulation of the left eye. The analysis of the effect of age on the latencies of the VERs revealed some interesting findings. As shown in Fig 2, the latencies of waves Nl increased with advancing age. Re¬ gression analysis of these data showed a greatly sloped regression line. The
highly significant (Í 7.34, .001). A similar highly significant increase of latency with aging was observed for wave PI (i 5.75, < .001) (Fig 3). The relationship between age and amplitude of the VERs is shown in Fig 4 and 5. There was no significant effect of age on the amplitude of waves Nl and PI. Similarly, there was no significant relationship between age
effect
=
was
LU 92
90 •
·#?···
88
86
84 -
0
10
20
AGE
30
IN
Fig 3.—Peak latency distribution
40
50
60
70
(
YEARS of
wave
P1 in relation to age.
Downloaded From: http://archneur.jamanetwork.com/ by a University of Pennsylvania User on 06/19/2015
limited to the VER latencies; it also influenced the critical frequency of
response expressed in flashes per second (Fig 6). CFPD was inversely correlated with age. The mean value between ages 20 and 30 was 72 flashes per second; between ages 30 and 60, 68; above age 60, 60 f. Regression analysis of these changes confirmed their statistical signifi¬
photic driving
cance
(i
=
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Daly,
Responses
MD
\s=b\ The effects of aging on visual evoked responses (VER) and critical frequency of photic driving (CFPD) was studied in 74 volunteers aged 18 to 79. The amplitude of VER to pattern reversal stimulation did not vary with sex or age. The latencies of the first major negative and of the first major positive deflection of the VER were significantly delayed (P < .001) with advancing age. This increase of latency probably reflects a slowing of conduction velocity in the optic nerve or optic pathways or both. CFPD, defined as the highest frequency of photic driving response expressed in flashes per second, showed an inverse correlation, decreasing with age in older subjects. Critical frequency of photic driving is the electrophysiological counterpart of critical flicker fusion, which is known to decrease with advancing age. These data support the concept that aging influences the functions of specialized sensory
systems. (Arch Neurol 34:403-407, 1977)
utilized: 02-A2; Ol-Al; Oz-Al; Oz-A2; 02-P4; 01-P3; Oz-Pz; and Oz-Cz. The input from the electrodes was fed into four preamplifi¬ ers adjusted to a bandwidth of 0.3 Hz to 1 kHz. The output was fed simultaneously into an averager and an oscilloscope. Writeouts from the averager were made with an X-Y plotter. The subject was comfortably seated on
the
electroencephalogram recording chair
1 m from a translucent screen on which the pattern was projected from the rear. A visual generated a checkerboard patterned stimulus in which dark and bright squares rhythmically exchanged their positions. The whole stimulating field subtended an angle of 9.3° with each indi¬ vidual check of the checkerboard subtend-
Fig 1.—Pattern reversal evoked responses in two left (OS) eyes. LD indicates latency difference latency in milliseconds of wave P1.
controls (A and B) from right (OD) and for wave P1. Numbers indicate peak
OD
is known that the conduction
It velocity of peripheral grad¬ advancing age.1·2 ually decreases nerves
with This phenomenon is attributed to a loss of large fibers and/or to segmen¬ tal demyelination of some axons.3·4 Central nervous system pathways may be similarly affected by the aging process. To test this possibility, visual evoked responses (VER) and critical frequency of photic driving (CFPD) were studied in 74 volunteers aged 18 to 79.
92.8
96.2
OS
METHOD Silver-silver chloride electrodes were applied to the scalp with collodion according to the 10-20 International System. Electrode impedance was below 5,000 . The following montages were
Accepted for publication Feb 23, 1977. From the Department of Neurology, St Louis University and the Veterans Administration Hospital (Dr Celesia); and the Department of Neurology, University of Wisconsin Center for Health Sciences, Madison (Dr Daly). Reprint requests to Department of Neurology, St Louis University, 1221 S Grand Blvd, St Louis, MO 63104 (Dr Celesia).
Downloaded From: http://archneur.jamanetwork.com/ by a University of Pennsylvania User on 06/19/2015
96.4
5 +
LD
:
0.2
µ
ing 15.5 minutes of arc measured at the subject's eye. The luminance of the pattern
stimulation was 10 foot-lamberts. Stimulation was carried out in a partially darkened room with background lumi¬ nance of 0.01 foot-lamberts. Subjects were instructed to remain still and fixate on a black dot at the center of the screen. Flashes were generated by a photic stimu¬ lator set at intensity "1." A stroboscope was placed 45 cm in front of the subject's eye. Stimulation began at a low frequency of flashes and was gradually increased until no photic driving could be obtained. The increments in the frequency of flashes
Visual Evoked Responses to Pattern Reversal Checks of 15.5' Subtense Peak Latencies Peak Latency,
Stimulation of Right Eye
Electrode N1
02-P4
N1
P1
01-P3
Mean 73.7
Range
Position Oz-Pz
N1 P1
67.2-89.6 89.6-116.8 67.2-89.6 92-116.8 67.2-89.6 92-116.8
100.9 73.8 100.1
73.8 100.1
msec
Stimulation of Left
Range 68.8-87.2 90.4-116 68.8-87.2 89.6-116 68.8-87.2 89.6-116
Eye
Mean 73.7 99.3 73.5 98.9 73.9
~99
stepwise as follows: 15, 20, 25, 31, 40, 50, 62, 76, 85, 90,100. Two hundred fifty-six
were
samples were averaged over 204.8 msec immediately following the pattern reversal or a flash. Only for flash stimulation equal or
above 50 flashes per second were 512 further improve the
samples summated to signal to noise ratio.
Pattern stimulation always preceded flash stimulation. Pattern stimulation was carried out with natural pupils, while flash stimulation was undertaken after the pupils were dilated with synephrine 2.5% solution. Monocular stimulation was used. Every volunteer had normal findings on neurological and ophthalmological exami¬ nation and agreed to participate in the study with full knowledge of the exper¬ imental nature of the research.
RESULTS The ages of the 74 volunteers ranged from 18 to 79 years, with a mean of 38.4 and a median of 31 years. There were 40 women and 34 men. Sixteen subjects wore corrective lenses during testing, but did not require more than +1.5 diopter cor¬ rection to achieve 20/20 visual acuity. The remainder had normal visual acuity without corrective lenses. Evoked responses to pattern rever¬ sal consisted of a major negative wave (Nl) with a mean peak latency of 73.7 msec followed by a major positive wave (PI) with a mean peak latency of 97.8 msec (Fig 1). Wave Nl was occa¬ sionally preceded by a small positive wave.
Referential and bipolar recordings compared in 20 volunteers. The amplitude of VERs from 02-A2, 01-A1, and Oz-Cz was larger than VERs from 02-P4, 01-P3, and Oz-Pz, but quite similar to responses obtained from OzCz. Muscle contamination was a frequent problem in referential re¬
were
cordings; therefore,
we
arbitrarily
limited our study to bipolar record¬ ings. No significant differences were seen in the peak latencies of the VERs
AGE
IN YEARS
Fig 2.—Peak latency distribution of wave N1 in relation to age. Lower line is regression line; upper line is limit of normal set at 2.5 times standard deviation of regression line. Numbers indicate value occurring repeatedly at same point on
graph.
Downloaded From: http://archneur.jamanetwork.com/ by a University of Pennsylvania User on 06/19/2015
among the midline and lateral
occip¬ ital recordings (Table). Also, the peak
latencies of VERs obtained with stim¬ ulation of the right eye were similar to those obtained with stimulation of the left eye. The analysis of the effect of age on the latencies of the VERs revealed some interesting findings. As shown in Fig 2, the latencies of waves Nl increased with advancing age. Re¬ gression analysis of these data showed a greatly sloped regression line. The
highly significant (Í 7.34, .001). A similar highly significant increase of latency with aging was observed for wave PI (i 5.75, < .001) (Fig 3). The relationship between age and amplitude of the VERs is shown in Fig 4 and 5. There was no significant effect of age on the amplitude of waves Nl and PI. Similarly, there was no significant relationship between age
effect
=
was
LU 92
90 •
·#?···
88
86
84 -
0
10
20
AGE
30
IN
Fig 3.—Peak latency distribution
40
50
60
70
(
YEARS of
wave
P1 in relation to age.
Downloaded From: http://archneur.jamanetwork.com/ by a University of Pennsylvania User on 06/19/2015
limited to the VER latencies; it also influenced the critical frequency of
response expressed in flashes per second (Fig 6). CFPD was inversely correlated with age. The mean value between ages 20 and 30 was 72 flashes per second; between ages 30 and 60, 68; above age 60, 60 f. Regression analysis of these changes confirmed their statistical signifi¬
photic driving
cance
(i
=
4.84,
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