Open Journal of Depression
2013. Vol.2, No.4, 82-86
Published Online November 2013 in SciRes (http://www.scirp.org/journal/ojd) http://dx.doi.org/10.4236/ojd.2013.24014
Mesopic Visual Contrast Sensitivity in Patients with Major
Renata M. T. B. L. Nogueira1*, Everton L. Espínola2, Aline M. Lacerda2,
Natanael A. Santos2
1Departamento de Psicologia da Universidade Federal de Pernambuco (UFPE), Recife, Brasil
2Laboratório de Percepção, Neurociências e Comportamento, Departamento de Psicologia, Universidade Federal
da Paraíba (UFPB), João Pessoa, Brasil
Received October 3rd, 2013; revised November 3rd, 2013; accepted November 11th, 2013
Copyright © 2013 Renata M. T. B. L. Nogueira et al. This is an open access article distributed under the Crea-
tive Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any me-
dium, provided the original work is properly cited.
The present study evaluated the effects of major depression on visual contrast sensitivity (CS) at low
mesopic luminance (.7 cd/m2 mean luminance), a condition that has been little explored in the literature.
We measured spatial visual CS in 20 male volunteers aged 20 - 30 years, including 10 healthy individuals
and 10 medicated individuals with major depression, to linear sine-wave gratings of .25, 1.0, and 4.0
cycles per degree (cpd) of visual angle using the psychophysical staircase method with forced choice. The
average spatial visual CS in the depressed group was approximately 1.7 lower than the average spatial
visual CS in the control group. However, the post hoc test showed significant differences only at the
spatial frequencies of .25 and 1.0 cpd (p < .05), which are likely processed by the magnocellular visual
pathway. These results suggest that spatial visual CS to sine-wave gratings should be used to evaluate the
responsiveness of the visual system in patients with major depression under conditions of low luminance.
Keywords: Visual Perception; Contrast Sensitivity; Depression; Spatial Frequency; Psychophysics
Depression can be defined as a mental disorder presented by
depressed mood, loss of pleasure and interest, feelings of guilt
and low self-esteem, sleep and appetite disturbances, low en-
ergy, and poor concentration (WHO, 2012). The annual inci-
dence of depression makes it one of the most important public
health problems, with severe socioeconomic implications, high
costs for health care, and a reduction of quality of life (Solomon,
2002). According to the World Health Organization (WHO,
2001), severe depression is the leading cause of disability and
ranks fourth among the 10 leading causes of pathology world-
wide. In fact, by 2020, depression is estimated to be the second
leading cause of disability worldwide. Studying depression us-
ing different approaches can complement clinical research and
contribute to the characterization of the basic cognitive, affec-
tive, and neurophysiological mechanisms of this disease. It may
also reveal new theoretical, behavioral, and functional aspects of
depression in general and highlight alternative means of diagnosis
and prognosis. The present study used visual contrast sensitivity
(CS) to assess the perception of patients with major depression.
Visual CS is one of the most widely used tools in the diagno-
sis and theoretical and clinical evaluation of changes in visual
perception and alterations in the central nervous system (Wes-
ner & Tan, 2006) caused by disorders or diseases, such as
schizophrenia (Slaghuis & Thompson, 2003), amblyopia (Polat,
Sagi, & Norcia, 1997), cataracts (Elliott & Situ, 1998), mercury
poisoning (Ventura et al., 2005), stroke (Santos & Andrade, 2012;
Santos, Andrade, & Fernandez Calvo, 2013), and Alzheimer’s
and Parkinson’s diseases (Polat et al., 1997; Akutsu & Legge,
1995; Bour & Apkarian, 1996; Vleugels et al., 1998).
Surveys related to visual CS and affective disorders are still
sparse, with only a few studies performed under different con-
ditions and for different purposes (Wesner & Tan, 2006; Ca-
valcanti & Santos, 2005; Szabó et al., 2004). For example,
Szabó et al. (2004) measured visual CS in volunteers with and
without seasonal affective disorder using static and dynamic
sine-wave gratings with spatial frequencies from .5 to 14.4
cycles per degree (cpd) of visual angle. The aim of that study
was to investigate the therapeutic effects of light therapy on
seasonal depression. The results showed that light therapy sig-
nificantly improved visual CS in patients at static spatial fre-
quencies below 5.7 cpd.
In a pilot study, Cavalcanti e Santos (2005) measured con-
trast thresholds in adult volunteers with and without major de-
pression under high photopic luminance conditions using
non-Cartesian radial visual stimuli at spatial frequencies of .25,
1.0, and 4.0 cpd. The results showed that patients with major
depression had a loss of or lower CS for all spatial frequencies
compared with volunteers without neuropsychiatric disorders.
Wesner & Tan (Wesner & Tan, 2006) measured contrast
thresholds in patients with seasonal depression and major de-
pression and volunteers without depression using static and
dynamic visual stimuli modulated by Gabor’s function with
spatial frequencies from .3 to 12 cpd under photopic luminance
R. M. T. B. L. NOGUEIRA ET AL.
Open Access 83
conditions. The results showed that participants with depression
had higher visual CS than the group without depression at high
static spatial frequencies of 6.0 and 12 cpd. The authors argued
that depression can increase the CS to frequencies that are pro-
cessed by the parvocellular visual pathway.
The present study evaluated the effects of major depression
on spatial visual CS by measuring achromatic visual CS in
adult volunteers with and without major depression using a
psychophysical method. The present study was motivated by
the assumption that depression alters the central nervous system
and affects numerous sensory, cognitive, and emotional func-
tion to promote changes in visual pathways (Wesner & Tan,
2006). Visual CS is an objective tool, noninvasive, and widely
used clinically to contribute to a greater understanding of the
sensory mechanisms associated with symptoms of depression.
Twenty 20- to 30-year-old male volunteers participated in the
study. Ten of the participants had no neuropsychiatric diseases
(mean age, 20.8 ± 1.2 years), determined by the Beck Depres-
sion Inventory, and 10 of the participants had a diagnosis of
major depression (mean age, 23.9 ± 4.0 years) according to the
Diagnostic and Statistical Manual of Mental Disorders, 4th
edition, text revision (American Psychiatric Association, 2000).
The patients with major depression were selected and ranked by
psychiatrists from the Centro de Atenção Psicossocial (CAPS;
João Pessoa, Paraíba, Brazil) and were taken to the Laboratório
de Percepção, Neurociências e Comportamento where the vis-
ual tests were conducted. Additional information about the pa-
tients with major depression is presented in Table 1.
All of the volunteers had normal visual acuity of 6/6 (inclu-
sion criterion) tested with directional “E” Rasquin optotype
cards (Xenônio, São Paulo, SP, Brazil) and were free of eye dis-
eases and neurological disorders (exclusion criterion), with the
exception of major depression or disorders related to major depres-
sion. The participation of the volunteers conformed to ethical as-
pects relevant to research that involves human subjects (National
Health Council Resolution no. 196/96, Health Ministry, Brazil). The
protocol was submitted to and approved by the Ethics Committee of
the Health Sciences Center, Universidade Federal da Paraíba. The
participation of the volunteers was voluntary and occurred only
after written informed consent was provided by them.
Visual Stimuli and Equipment
The test stimuli were achromatic linear sine-wave gratings
(.7 cd/m2 mean luminance) with spatial frequencies of .25, 1.0, and
4.0 cpd. The non-test stimuli were gray and contained only the
mean luminance. The diameter of the resulting patterns subtended
approximately 7.2 degrees at a distance of 150 cm (i.e., the stan-
dardized distance between the monitor and volunteer). Contrast
was defined according to Michelson’s formula (Michelson, 1891):
CLxmax LxminLxmax Lxmin
x is the luminance at a given point on the sine wave,
with x measured radially from the center.
xmin are the maximum and minimum luminances of the
pattern, respectively. C is the contrast. The spatial average lu-
minance of the grating is given by
The stimuli were presented on a 19-inch color cathode ray
tube video monitor (1024 × 768 resolution, 70 Hz refresh rate).
The stimuli were controlled by a computer through VGA and
DVI video connectors. The dynamic range of the contrasts that
the monitor could present was expanded more than 64 times by
a BITS++ digital video processor (Cambridge Research Sys-
tems, Rochester, Kent, England, 2002), resulting in 14 bits per
channel or 42 bits per pixel, allowing the presentation of more
than 16,384 (or 214) grayscale levels. This allowed the testing of
contrast thresholds while enabling high-contrast resolution. The
BITS++ processor was controlled by C++ software developed
by our research group. It generated and controlled the stimulus
presentation and recorded the observer responses to calculate
contrast threshold values.
The monitor was calibrated with LightScan software and an
optical photometer (Cambridge Research Systems, Rochester,
Kent, England, 2002). The monitor output was gamma-cor-
rected using 48 points from 0 to 255 (gamma = 1.8). The mi-
nimum and maximum luminance values of the screen were .5
and .9 cd/m2, respectively, and the background luminance was
the minimum luminance itself. The laboratory room was 2.5
2.0 m, with one Philips 20W fluorescent lamp. The walls were
gray to better control ambient lighting during the experiment.
Characterization of the experimental group.
Patient* Age (Years)
Inventory Time of Disease
(Years) Sex Drug Education
P1 23 Moderate depression2 Female Fluoxetine Graduate
P2 20 Moderate depression2 Female Fluoxetine Academic
P3 26 Moderate depression2 Male Fluoxetine Academic
P4 22 Moderate depression1 Female Fluoxetine Academic
P5 30 Severe depression 2 Female Fluoxetine Academic
P6 19 Mild depression 1 Female Risperidone Academic
P7 28 Severe depression 2 Female Venlafaxine, Clonazepam, Zolpidem Academic
P8 29 Moderate depression2 Female Floral de Bach Graduate
P9 22 Moderate depression1 Female No drug Academic
P10 20 Mild depression 1 Male No drug Graduate
*The characteristics of the participants in the control group (i.e., age, sex, and education level) were similar to the experimental group. See the average ages of the two
groups in the Participants section.
R. M. T. B. L. NOGUEIRA ET AL.
The participants viewed the stimuli binocularly with natural
pupils at a distance of 150 cm. A fixed chair and forehead-chin
support were used to control the viewing distance. The visual
CS of all of the participants was estimated using a temporal
two-alternative forced-choice staircase method (Wetherill &
Levitt, 1965). The procedure for measuring the threshold for
each frequency consisted of presenting successive pairs of sim-
ple stimuli, one of which was the test stimulus that should be
identified by the participant (i.e., the first or second stimulus of
each pair). The order of the presentation of the stimuli and fre-
quencies was randomized by the software. The criterion used to
alternate the contrast during the experimental session was three
consecutive hits to reduce contrast by 20%, and one error to
increase contrast by the same percentage.
Threshold measurements began with the test stimulus con-
trast set at a suprathreshold level (contrast = 1). Each time the
volunteer gave a correct answer, the contrast was decreased
successively until he made an error. The software recorded the
last perceived contrast value. The contrast was then raised until
the volunteer could perceive the stimulus again. In this case, the
software recorded the first perceived contrast value. The ex-
perimental session automatically ended after the software re-
corded six staircase contrast values. Each threshold measure-
ment was repeated for each spatial frequency. The contrast
threshold calculated for each volunteer was the mean of the 12
contrast values (six at the test and six at the retest).
A stimulus sequence was presented during each experi-
mental session, starting with a beep and followed immediately
by the presentation of the first stimulus for 2 s. A 1 s interval
elapsed between stimuli, followed by the presentation of the
second stimulus for 2 s and the volunteer’s response. All of the
participants responded within the 3-s interval. A correct re-
sponse was followed by another beep. The interval between
trials was 3 s, regardless of a correct or incorrect response (or
choice). The beeps that indicated the beginning of the stimulus
pair presentation and correct choice were different.
All of the participants received the following instructions:
“Pairs of circles will appear on the screen, one after the other.
One of them will be totally gray, whereas the other will contain
light and dark gratings (bars) inside it. When the circle with
light and dark gratings (bars) appears first, you must press the
left mouse button (button 1); when the circle with light and
dark gratings (bars) appears second, you should press the right
mouse button (button 2).”
The experiments began only when the experimenter was
confident that the participants understood and responded ac-
cording to the directions. In this context, instructions were re-
peated in a training and familiarization session with the ex-
After each experimental session, the software produced a re-
cord sheet with the 12 staircase contrast values from each par-
ticipant, six in the test and six in the retest. Values were
grouped according to mental condition (i.e., participants with-
out major depression [control group] and participants with ma-
jor depression [experimental group]). All of the staircase con-
trast threshold values were converted into CS values (1/thresh-
All 240 staircase contrast values (12 from each volunteer) for
each spatial frequency were used to conduct a Tukey Two-
Sided Outlier Test. The 3, 4, and 8 outlier values for .5, 1.0, and
4.0 cpd, respectively, identified by the Tukey test were set to
equal the group mean calculated in the absence of the outlier.
After the Tukey Outlier Test, the means of the staircase contrast
values were used to calculate their individual linear CS values.
A one-way analysis of variance (ANOVA) applied to CS re-
vealed significant differences between groups (F3,396 = 80.5, p
< .05) and a significant interaction (F3,396 = 905.2, p < .05).
Thus, the control and experimental groups had different con-
trast sensitivity (p < .05).
The Tukey Honestly Significant Difference post hoc test
showed significant differences between the groups only at low
spatial frequencies of .25 and 1.0 cpd (p < .05). The differences
between groups at the spatial frequency of 4.0 cpd were not
significantly different (p > .05). The participants with major
depression generally required higher contrast to detect the spa-
tial frequencies of .25 and 1.0 cpd than the participants without
any neuropsychiatric disease.
The results showed that the maximum CS in the control
group occurred at frequencies of .25 and 1.0 cpd, whereas the
maximum CS in the experimental group occurred at the fre-
quency of .25 cpd (Figure 1). The data also showed that the
participants without any neuropsychiatric disease were 1.57-,
2.14-, and 1.28-times more sensitive to spatial frequencies
of .25, 1.0, and 4.0 cpd, respectively, than the patients with
The present study measured visual CS using a psychophysi-
cal staircase method, with forced choice between two temporal
alternatives under mesopic luminance conditions. The research
hypothesis was that major depression would alter the response
of the visual system or the basic sensory mechanisms involved
in processing visual patterns, altering contrast sensitivity to
sine-wave gratings with spatial frequencies of .25, 1.0, and 4.0
The estimated contrast sensitivity in adult volunteers is presented as a
spatial frequency function of .25, 1.0, and 4.0 cpd. The continuous
curve (─■─) represents the control group (without major depression),
and the dotted curve (---▲---) represents the experimental group (with
major depression). The error bars indicate standard errors of the mean
(p = .05).
R. M. T. B. L. NOGUEIRA ET AL.
Open Access 85
Major depression likely does not equally interfere with the
anatomical and physiological mechanisms related to the proc-
essing of the tested visual spatial frequencies. The decrease
observed in visual spatial CS in patients with major depression
was statistically significant only at the low spatial frequencies
(.25 and 1.0 cpd), which are probably processed preferentially
by the magnocellular visual pathway, especially when consid-
ering low luminance used in the study (Lee, Martin, & Valberg,
1989; Livingstone & Hubel, 1987; Murray, Parry, & Carden,
1987; Valberg & Rudvin, 1997; Vassilev, Stomonyakov, &
Manahilov, 1994). According to Souza et al. (2007), at low
spatial frequencies of .4 - .8 cpd, only the magnocellular visual
pathway appears to be relevant for the cortical response. No
significant differences in CS were found between the control
group and experimental group at the highest spatial frequency
tested (4.0 cpd). Therefore, major depression may preferentially
damage the magnocellular visual pathway rather than affect the
mechanisms that process high spatial frequencies, which may
involve the parvocellular visual pathway. This hypothesis relies
on the possibility that magnocellular channels are activated by
spatial frequencies below 2.0 cpd, whereas parvocellular chan-
nels are activated by spatial frequencies above 4.0 cpd (Adams
& Courage, 2010; Burbeck & Kelly, 1981). Importantly, how-
ever, the levels of scotopic and photopic contrast appear to be
the dominant factor for the functional activity of the magnocel-
lular and parvocellular pathways, respectively, rather than the
spatial frequency itself (Skottun & Skoyles, 2011).
We cannot definitively state that the alterations found in vis-
ual perception or CS solely resulted from changes in the central
nervous system produced by major depression. Other factors
are likely involved. For example, antidepressants, such as flu-
oxetine, venlafaxine, and others, act by modulating the func-
tion of the central nervous system. The present study did not
seek to control the effects of antidepressants on visual CS
measures. Typical and atypical antipsychotic medications can
also differentially change perceived contrast (Chen et al., 2003).
Changes in visual CS caused by major depression were ex-
pected in the present study, based on studies that reported that
neuropsychiatric disorders affect cognition and central nervous
system function (Bubl et al., 2010; Duman, Heninger, & Nes-
tler, 1997; O’Donnell et al., 2002; Slaghuis, 1998; Wolman &
Stricker, 1990). Some studies used electrooculography (EOG)
(Lam et al., 1991; Fountoulakis, Foutiou, Iacovides, & Kaprinis,
2005) and flash electroretinography (ERG) (Fountoulakis et al.,
2005; Hébert et al., 2004; Lavoie et al., 2009) to evaluate pa-
tients with seasonal depression and reported the presence of
changes in the retina at the photoreceptor level, which resulted
in decreased light sensitivity in depressive patients compared
with the control group. Both EOG and ERG are useful tools,
the results of which indirectly reflect dopamine activity in the
retina. Several studies have related decreased dopamine activity
with specific depressive symptoms. For example, Harris, Cal-
vert, Leendertz e Phillipson (1990) suggested that lower dopa-
mine levels in the brain in depressed patients result in a de-
crease in visual CS. Bodis-Wollner e Tzelepi (1998) proposed
that dopamine D2 receptors affect the ability to visually detect
high spatial frequencies, whereas D1 receptors affect the ability
to visually detect low spatial frequencies. These authors argued
that decreased dopamine levels could attenuate the inhibition
modulated by horizontal cells, which are involved with the
perception of visual CS, thus resulting in a reduction of this
Szabó et al. (2004) reinforced the hypothesis that major de-
pression damages the magnocellular visual pathway. These
authors found a decrease in CS at a low spatial frequency (.5
cpd). However, these results are different from the results re-
ported by Wesner e Tan (2006), who found no losses in visual
CS in patients with depression but greater CS to higher spatial
frequencies. The authors argued that depression can increase
the CS to spatial frequencies processed by the parvocellular
visual pathway. However, Wesner e Tan (2006) used different
stimuli (i.e., a gabor patch) and luminance, rendering direct
comparisons between their results and the present study diffi-
The present study investigated whether major depression al-
ters visual CS at low levels of luminance. The results showed a
reduction of CS in patients with major depression compared
with healthy volunteers who were matched for age, sex, and
educational level. However, unclear is whether the changes
observed were caused by depression itself, medications, or a
combination of both. Only three of the 10 participants in the
experimental group did not use medications. Finding patients
with major depression who use only a single medication is dif-
ficult, but new research needs to systematically investigate the
effect of medication on visual spatial CS. Overall, the present
data suggest that major depression caused changes in the mag-
nocellular pathway, a pathway that is important in the process-
ing of spatial frequencies under low luminance conditions.
We thank all of the volunteers who participated in this re-
search and the psychiatrists from the Centro de Atenção Psi-
cossocial (CAPS; João Pessoa, Paraíba, Brazil) who diagnosed
the patients with major depression. Research was supported by
CNPq # 303822/2010-4.
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