THE RELATIONSHIP BETWEEN ACUTE MOOD, SLEEP, AND SEX ON NEUROCOGNITIVE PERFORMANCE POST-CONCUSSION IN ADOLESCENTS

Background: Both sleep disturbance and mood changes are common symptoms post-concussion (Sell & Rubeor, 2017). Studies have found these symptoms are correlated with poorer performance on neurocognitive testing (Kontos et al., 2012 and Kostyun et al., 2015). In addition, Brown et al., (2015) showed that females report more symptoms at both baseline and post-concussion compared to males on the Post-Concussion Scale and the Sport Concussion Assessment Tool 2. Hypothesis/Purpose: The purpose of this study is to investigate how a patient’s sex, as well as self-reported acute mood and sleep symptoms are related to neurocognitive performance in individuals with concussion. Methods: Data were acquired through IRB-approved retrospective chart review. Composite scores from the Immediate Post-Concussion Assessment and Cognitive Testing (ImPACT) computerized evaluation and self-reported symptom scores on the Post-Concussion Symptom Scale were gathered for 1619 adolescents age 12-18 (49.3% female) who presented to a large metropolitan outpatient clinic for treatment of concussion. Results: Females endorsed higher overall symptoms (x=19.52, SD 19.37, median 13.0 for females; x=12.88, SD 15.89, median 7.0 for males; Mann-Whitney U Test p<0.001). This same pattern emerged for the mood and sleep symptom clusters (female mood mean=2.92, SD 4.51; male mood mean=1.64, SD 3.34; female sleep mean=1.59, SD 2.0; male sleep mean=1.11, SD 1.84; both Independent Samples Mann-Whitney U Tests ps<0.001). There were significant but modest negative correlations between mood symptoms and performance on verbal memory (r=-0.174), visual memory (r=-0.213), and visual motor speed (r=-0.146) composites (all ps<0.01). There was positive correlation between reaction time composite and mood symptoms (r=0.191). There were significant but modest negative correlations between sleep symptoms and performance on verbal memory (r=-0.171), visual memory (r=-0.184), and visual motor speed (r=-0.161) composites (all ps<0.01). There was a positive correlation between reaction time composite and sleep symptoms (r=0.196, p<0.01). Conclusion: Consistent with prior research, adolescent females reported more symptoms post-concussion, including total symptom score, mood symptoms, and sleep symptoms. Adolescents presenting with more mood and sleep symptoms demonstrated poorer performance on neurocognitive testing. However, given the modest nature of the correlation, a significant amount of variation in test performance is not explained by symptom report. Results from this study underscore the importance of a multidimensional concussion assessment that includes both symptom report and cognitive testing when working with pediatric athletes. This study also reinforces the importance of understanding potential effects of sleep, mood, and sex on concussion.

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A-120 Comparison of Baseline and Post-Concussion ImPACT Performance in Spanish-English Bilingual and English Monolingual Athletes

Archives of Clinical Neuropsychology ◽

10.1093/arclin/acab062.138 ◽

2021 ◽

Vol 36 (6) ◽

pp. 1170-1170

Author(s):

Erick Rogers ◽

Hana Kuwabara ◽

Grace Goodwin ◽

Sara Moore ◽

Nia Hopkins ◽

...

Keyword(s):

Reaction Time ◽

Visual Memory ◽

Cognitive Testing ◽

English Speakers ◽

Future Research ◽

Motor Speed ◽

Linear Modeling ◽

Impact Performance ◽

Sport Type ◽

Visual Motor

Abstract Objective Research comparing English and Spanish administrations of Immediate Post-Concussion Assessment and Cognitive Testing (ImPACT) have consistently found differences in performance on various cognitive composites. Few studies have examined the effect of bilingualism on baseline and post-concussion assessments. This study examined whether monolingual English-speakers (MO) and bilingual Spanish/English speakers (BI) differed in cognitive performance at baseline (BL) and post-concussion (PC). Methods Participants were selected from a larger database of high school athletes administered ImPACT in English at BL and PC. Participants included 86 BI athletes (Mage = 14.53; 65.10% male) and 86 MO athletes matched on age, gender, sport type, and probable concussion as defined by number of PC follow-up assessments (PCF; 0 vs. ≥1). To examine group differences and changes over time in cognitive composites, a general linear modeling approach was used with language and PCF as between-subjects factors and time as a within-subjects factor. Results There was a significant Language x Time x PCF interaction for Visual Memory (VM), Visual Motor Speed (VMS), and Reaction Time (RT). On VM and RT, MO with multiple PCF performed the worst at PC, while MO with 0 PCF performed the best at PC. On VMS, BI with 0 PCF performed the worst at BL. Conclusion Visual memory and reaction time were less affected in bilingual compared to monolingual athletes with probable concussion. However, at baseline, bilingual athletes had slower visual motor speed compared to monolingual athletes. Future research should focus on how bilingualism may serve as both a protective and risk factor for cognitive functioning after probable concussion.

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B-44 An Examination of Balance Measurements in Predicting Post-Concussion Neurocognitive Dysfunction

Archives of Clinical Neuropsychology ◽

10.1093/arclin/acz034.127 ◽

2019 ◽

Vol 34 (6) ◽

pp. 990-990

Author(s):

A DaCosta ◽

A Crane ◽

M Fasciana ◽

A LoGalbo

Keyword(s):

Reaction Time ◽

Verbal Memory ◽

Visual Memory ◽

Clinical Utility ◽

Collegiate Athletes ◽

Motor Speed ◽

Balance Performance ◽

Neurocognitive Dysfunction ◽

Balance Deficits ◽

Visual Motor

Abstract Objective Previous research indicates that athletes experiencing concussions demonstrate acute balance deficits (Guskiewicz, 2011). Although it is hypothesized that balance performance is related to neurocognitive function in athletes experiencing a concussion (Guskiewicz, Ross, & Marshall, 2001; Broglio, Sosnoff, Ferrara, 2009), limited research exists regarding the clinical utility of baseline measures. Method 68 collegiate athletes (ages 18-23; M = 19.62, SD = 1.44) were evaluated using the Balance error scoring system (BESS) and ImPACT at baseline and post-concussion. Multiple linear regressions were used to determine how BESS performance change across evaluations predicted post-concussion neurocognitive dysfunction compared to post-concussion performance alone. Results BESS performance changes from baseline to post-concussion significantly predicted post-concussion Verbal Memory (R² = .06, p = .05), Visual Memory (R² = .135, p = .002), Visual-Motor Speed (R² = .146, p = .001), Reaction Time (R² = .156, p = .001), and Total Symptom Scores (R² = .112, p = .005); while post-concussion BESS scores predicted Visual Memory (R² = .138, p = .002), Visual-Motor Speed (R² = .137, p = .002), and Reaction Time (R² = .145, p = .001). Therefore, assessing change in BESS performance is a more comprehensive predictor of neurocognitive dysfunction than solely post-concussion BESS performance. Conclusions Changes in BESS performance from baseline to post-concussion was found to be a more comprehensive predictor of neurocognitive dysfunction than post-concussion BESS scores alone. Therefore, our results support the clinical utility of evaluating balance at pre-participation to better understand neurocognitive risk factors.

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A - 08 Within Subjects Comparison of Clinical Outcomes After First, Second, and Third Concussions in Adolescents*

Archives of Clinical Neuropsychology ◽

10.1093/arclin/acab035.08 ◽

2021 ◽

Vol 36 (4) ◽

pp. 648-648

Author(s):

Feder AH ◽

French J ◽

Blaney N ◽

Eagle SR ◽

Kontos AP

Keyword(s):

Clinical Outcomes ◽

Verbal Memory ◽

Visual Memory ◽

Recovery Time ◽

Cognitive Test ◽

Motor Speed ◽

Neurocognitive Performance ◽

Symptom Scale ◽

Visual Motor ◽

Improved Performance

Abstract Objective The objective of the current study was to examine differences in clinical outcomes between adolescents’ first, second, and third concussions. Methods We conducted a retrospective medical chart review of adolescents (n = 40) aged 10–19 years-old (M = 13.0;SD = 1.9;56% male) who presented for evaluation of concussion at a specialty clinic for their first (Concussion 1 = C1), second (C2), and third (C3) concussions. Clinical outcomes included Immediate Post-Concussion Assessment and Cognitive Test (ImPACT), Post-Concussion Symptom Scale (PCSS), Vestibular/Ocular-Motor Screening (VOMS) scores from the first clinic visit for each injury, recovery time, and days between injuries. Paired samples t-tests were conducted to compare outcomes between concussions. Results When comparing initial presentation between C1 and C2, participants demonstrated no significant differences in ImPACT, PCSS (t[38] = 0.85, p = 0.402) or VOMS (t[34] = −0.75, p = 0.461), with the exception of faster Visual Motor Speed for C2 (t[38] = −3.45, p = 0.001). Participants demonstrated improved performance from C1 to C3 on ImPACT composites of Verbal Memory (t[38] = −4.22, p < 0.001), Visual Memory (t[38] = −2.99, p = 0.005), Visual Motor Speed (t[38] = −5.14, p < 0.001) and Reaction Time (t[38] = 0.11, p = 0.001). Symptom report was consistent on PCSS (t[38] = 1.80, p = 0.081) and VOMS (t[30] = −0.12, p = 0.903) between C1 and C3. Recovery time was similar comparing C1 to C2 (t[36] = −0.35,p = 0.725) and C1 to C3 (t[34] = 1.74,p = 0.090). Conclusions The results suggest adolescents demonstrate similar levels of symptoms, VOMS, and recovery time after first, second, and third concussions. Neurocognitive performance improved across C1 to C3, suggesting possible learning effect or improved performance with cognitive development. These results provide additional support for similarity between an athlete’s first and second concussion with further initial evidence that a third concussion does not result in worse outcomes.

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Acute Stimulant Ingestion and Neurocognitive Performance in Healthy Participants

Journal of Athletic Training ◽

10.4085/1062-6050-50.1.07 ◽

2015 ◽

Vol 50 (5) ◽

pp. 453-459 ◽

Cited By ~ 2

Author(s):

Michael E. Powers

Keyword(s):

Reaction Time ◽

Attention Deficit Disorder ◽

Visual Processing ◽

Visual Memory ◽

Efficiency Index ◽

Cognitive Testing ◽

Motor Speed ◽

Neurocognitive Performance ◽

Cognitive Efficiency ◽

And Control

Context Concussion management has become an area of great concern in athletics, and neurocognitive tests, such as Immediate Post-Concussion Assessment and Cognitive Testing (ImPACT), are commonly used as management tools. Given the restrictive nature of current management plans, anecdotal concerns have been raised about athletes trying to cheat the assessments and return to participation sooner. Stimulants have been shown to improve neurocognitive measures similar to those used in ImPACT. Therefore, they could possibly improve performance during baseline and postinjury testing. Objective To examine the effects of a supplement containing stimulants on ImPACT performance. Design Crossover study. Setting Research laboratory. Patients or Other Participants A total of 5 men (age = 20.6 ± 1.5 years, height = 176.3 ± 9.6 cm, mass = 76.9 ± 18.6 kg) and 7 women (age = 20.6 ± 1.1 years, height = 162.9 ± 7.8 cm, mass = 60.9 ± 8.2 kg) with no histories of physician-diagnosed head injury, learning disability, or attention-deficit disorder. Intervention(s) Participants were assessed under supplement (5.5 g of Jacked 3D, which contains caffeine and 1,3-dimethylamylamine), placebo, and control conditions separated by 1 week. Main Outcome Measure(s) I compared ImPACT composite scores for verbal and visual memory, visual motor speed, reaction time, impulse control, and a cognitive-efficiency index under each of the 3 conditions and assessed them 30 minutes after ingestion. Results I observed a difference when comparing reaction times, as the participants reacted faster during the supplement condition (0.53 ± 0.03 seconds) than during the placebo (0.55 ± 0.03 seconds) and control (0.55 ± 0.03 seconds) conditions (F2,22 = 4.31, P = .03). A difference also was observed for the cognitive-efficiency index, as participants scored higher during the supplement condition (0.49 ± 0.09) than during the placebo (0.41 ± 0.10) and control (0.41 ± 0.12) conditions (F2,22 = 4.07, P = .03). Conclusions Stimulant ingestion 30 minutes before testing resulted in improved memory, visual processing speed, and reaction time. However, the improvements were relatively nominal, and the question of clinical importance remains. Thus, it is unclear if stimulant ingestion would affect the return-to-participation progression.

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Self-Reported History of Seizure, Baseline Neurocognitive Performance, and Symptoms Reported in High School Athletes

Archives of Clinical Neuropsychology ◽

10.1093/arclin/acz026.47 ◽

2019 ◽

Vol 34 (5) ◽

pp. 777-777

Author(s):

A Datoc ◽

L Lashley

Keyword(s):

High School ◽

Visual Memory ◽

Cognitive Testing ◽

Group Differences ◽

Motor Speed ◽

Neurocognitive Performance ◽

High School Athletes ◽

History Of ◽

Visual Motor ◽

Literature Highlight

Abstract Purpose To examine whether a self-reported history of seizure is associated with differences in baseline neurocognitive performance and total reported symptoms. Methods Data was derived from a de-identified Immediate Post-Concussion Assessment and Cognitive Testing (ImPACT) database of high school athletes in Florida. After inclusion and exclusion criteria were applied, athletes were separated into groups dependent on self-reported history of seizure. 260 athletes (Mage=15.49, SD=1.26; 57.1% male) reported a history of seizure, and 260 athletes were randomly selected from those with no such history (Mage=15.64, SD=1.22; 61.1% male). Results ANOVA (alpha=.05) revealed significant differences between groups on the visual memory composite (F[1,559]=4.915, p=.027) and total symptom score (F[1,559]=28.596, p<.001) at baseline. Athletes with a self-reported history of seizure performed significantly worse than athletes without on visual memory and reported significantly higher total symptom scores. No significant between-group differences were found on the other composites of ImPACT. Conclusion The association between seizure history and decreased neurocognitive performance has been documented in the neuropsychological literature, and may be explained by differences at a microstructural level such as differences in white matter integrity (Yassine et al., 2018). While these microstructural differences have implications on cognitive functioning and symptomatology, the present study surprisingly found comparable scores between athletes with a history of seizure and those without. Previous researchers published similar findings; however, differences were observed on the visual-motor speed composite of ImPACT (Zalneraitis et al., 2017). The inconsistencies and small effect sizes in the present literature highlight the need for investigators to determine the clinical significance of these results in concussion evaluations.

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Signs of cognitive dysfunction in adult players of club level rugby

South African Journal of Psychology ◽

10.1177/0081246319826816 ◽

2019 ◽

Vol 50 (1) ◽

pp. 128-140 ◽

Cited By ~ 1

Author(s):

Diana Zoccola ◽

Ann B Shuttleworth-Edwards ◽

Sarah E Radloff

Keyword(s):

Reaction Time ◽

Cognitive Dysfunction ◽

Verbal Memory ◽

Visual Memory ◽

Rugby Union ◽

Motor Speed ◽

Visual Motor ◽

The Impact ◽

Rugby Players

The objective of this study was to investigate players of club level Rugby Union (hereafter rugby) over one rugby season, for signs of residual cognitive dysfunction due to repeated concussive events incurred during long-term participation in the sport. Adult male players of club level rugby, without a diagnosis of a concussion during the season ( n = 20), were compared with non-contact club level sports participants ( n = 22) of equivalent sex, age, education, and estimated IQ at pre-, mid-, and post-season intervals. Measures included the ImPACT Verbal Memory, Visual Memory, Visual Motor Speed and Reaction Time composites, and the Purdue Pegboard test. Statistical group comparisons revealed consistently poorer performance for rugby players compared with controls for ImPACT Visual Motor Speed and Reaction Time composites at all test intervals, and for the Purdue Pegboard tasks at the first two test intervals. Repeat measures comparisons across the three test intervals demonstrated differential learning patterns between groups on ImPACT Visual Memory, ImPACT Reaction Time, and Purdue Both tasks, suggestive of cognitive vulnerability in the rugby group. Overall, the results reveal deleterious cognitive performance in adult club level rugby players relative to equivalent non-contact sports controls. The finding serves to endorse indications from other studies that demonstrate persistent brain injury effects in association with long-term participation in a contact sport. Recommendations for further research and management of concussion in rugby players are discussed.

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A-38 A Different Approach for Examining Gender Differences on Computerized Neurocognitive Testing: Percentile Ranks Versus Composite Scores

Archives of Clinical Neuropsychology ◽

10.1093/arclin/acaa036.38 ◽

2020 ◽

Vol 35 (5) ◽

pp. 634-634

Author(s):

P Schatz ◽

K Slicer ◽

R J Elbin

Keyword(s):

Gender Differences ◽

Reaction Time ◽

Verbal Memory ◽

Visual Memory ◽

Motor Speed ◽

Age And Gender ◽

Visual Motor ◽

Gender Based ◽

And Gender ◽

Composite Scores

Abstract Objective ImPACT is a popular tool used to assess neurocognitive function after concussion. Age- and gender-based percentile ranks are provided as part of the ImPACT clinical report, but only raw composite scores are provided for research. Percentile ranks may provide an alternate look at gender differences on neurocognitive testing. We sought to compare the use of percentile ranks versus composite scores when comparing neurocognitive performance between male and females. Method Pre-season baseline data from 3,238 collegiate athletes were exported from a larger multi-site database, 1,714 male (53%) and 1,524 female (47%), ages 18–22 (Mean = 19.3, SD = 1.2). ImPACT composite scores were extracted (Verbal Memory, Visual Memory, Visual Motor Speed, Reaction Time) and Percentile Ranks were calculated using age- and gender-based reference tables in the ImPACT 2017–2012 Technical Manual. One-way analyses of variance (ANOVA) were conducted with gender as the IV and the four composite scores and their associated percentile ranks as the DVs. Bonferroni correction for 8 comparisons set the alpha level to p < .006. Results ANOVAs revealed a significant effect of gender on ImPACT Verbal Memory [F(1,3236) = 16.32, p < .001], Visual Memory [F(1,3236) = 66.06, p < .001], Visual Motor Speed [F(1,3236) = 15.61,p < .001] but not Reaction Time [F(1,3236) = 2.59, p = .11]. When using percentile ranks, ANOVAs revealed a significant effect of gender on only Visual Motor Speed [F(1,3236) = 31.07, p < .001], but not Verbal Memory [F(1,3236) = 2.43, p = .12], Visual Memory [F(1,3236) = 0.48, p = .49], or Reaction Time [F(1,3236) = 0.61, p = .44]. Conclusions Use of ImPACT Composite Scores in concussion research may exaggerate or inappropriately promote gender differences on computerized neurocognitive testing. Given that age- and gender-based normative data are available, use of percentile ranks is recommended.

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The Effect of Test Setting Upon Test-Retest Reliability of ImPACT Baseline Tests in High School Athletes

Neurology ◽

10.1212/01.wnl.0000801956.01474.ba ◽

2021 ◽

Vol 98 (1 Supplement 1) ◽

pp. S23.2-S23

Author(s):

Mark Thomas William Roberts ◽

Jonathan Danield Lichtenstein

Keyword(s):

High School ◽

Reaction Time ◽

Verbal Memory ◽

Visual Memory ◽

Motor Speed ◽

High School Athletes ◽

Retest Reliability ◽

Concussion Management ◽

Visual Motor ◽

Test Retest Reliability

ObjectiveTo determine the test-retest reliability of ImPACT baseline tests across different schools within the same larger concussion management program.BackgroundImPACT is the most widely used concussion management cognitive testing tool. Baseline testing is often required for high school sports participation. Typically, testing occurs every 2 years based on test-retest reliability statistics in previous studies. Demographic and environmental factors, such as age, sex, number of participants, and supervision, all impact baseline performance. Studies to date have not examined test-retest differences across testing sites, such as between school differences.Design/MethodsCross-sectional retrospective design. Valid baseline tests from high school athletes over a 2-year interval were included. Participants who experienced concussions prior to or between tests were excluded. A total of 979 student athletes from 5 schools were included. The Intra-class correlations were determined over a 2-year period for each ImPACT composite score and school.ResultsICC estimates averaged between schools reflected good reliability for visual-motor speed (0.833), visual memory (0.673) and reaction time (0.615) over the two-year period. Verbal memory (0.586) and impulse control (0.556) were less reliable. Between schools a greater range of composite reliability was observed for reaction time (0.484–0.730) and impulse control (0.461–0.655) compared to verbal memory (0.534–0.637), visual memory (0.61–0.719), and visual-motor speed (0.769–914).ConclusionsAs previously established, reliability of ImPACT baselines vary by composite. This study revealed that reliability also varies by setting, as different schools yielded different ICCs. Consistent with the literature, the most reliable measure was visual-motor speed. The greatest difference in reliability between schools was for reaction time. These results suggest that test setting and environment affect reliability of ImPACT baseline scores, with varying effects per composite. Attention must be paid to environmental setting to improve reliability of baseline cognitive test performance to maximize athlete safety.

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Concussion in Sports: Postconcussive Activity Levels, Symptoms, and Neurocognitive Performance

Journal of Athletic Training ◽

10.4085/1062-6050-43.3.265 ◽

2008 ◽

Vol 43 (3) ◽

pp. 265-274 ◽

Cited By ~ 240

Author(s):

Cynthia W. Majerske ◽

Jason P. Mihalik ◽

Dianxu Ren ◽

Michael W. Collins ◽

Cara Camiolo Reddy ◽

...

Keyword(s):

Reaction Time ◽

Verbal Memory ◽

Repeated Measures ◽

Visual Memory ◽

Student Athletes ◽

Activity Level ◽

Activity Levels ◽

Motor Speed ◽

Neurocognitive Performance ◽

Activity Intensity

Abstract Context: Evidence suggests that athletes engaging in high-intensity activities after concussion have more difficulties with cognitive recovery. Objective: To examine the role postinjury activity level plays in postconcussive symptoms and performance on neurocognitive tests in a population of student-athletes. Design: Retrospective cohort study with repeated measures of neurocognitive performance and symptom reporting. Setting: University-based sports concussion clinic. Patients or Other Participants: Ninety-five student-athletes (80 males, 15 females: age = 15.88 ± 1.35 years) were retrospectively assigned to 1 of 5 groups based on a postinjury activity intensity scale. Main Outcome Measure(s): We employed a regression analysis for repeated measures to evaluate the relationship of activity intensity to symptoms and neurocognitive outcome up to 33 days after concussion. Postconcussion symptom scores and neurocognitive (verbal memory, visual memory, visual motor speed, and reaction time) scores served as the primary outcome measures. Results: Level of exertion was significantly related to all outcome variables (P < .02 for all comparisons). With multivariate analysis, activity intensity remained significant with respect to visual memory (P = .003) and reaction time (P < .001). Conclusions: Activity level after concussion affected symptoms and neurocognitive recovery. Athletes engaging in high levels of activity after concussion demonstrated worse neurocognitive performance. For these tasks, those engaging in moderate levels of activity demonstrated the best performance.

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Addressing the ``Replication Crisis'' in Sports Neuropsychology: Validation of the Two-Factor Theory of ImPACT

Archives of Clinical Neuropsychology ◽

10.1093/arclin/acz026.28 ◽

2019 ◽

Vol 34 (5) ◽

pp. 758-758 ◽

Cited By ~ 1

Author(s):

P Schatz ◽

K Bogar ◽

R J Elbin

Keyword(s):

High School ◽

Reaction Time ◽

Factor Structure ◽

Verbal Memory ◽

Visual Memory ◽

Impact Testing ◽

Memory Factor ◽

Speed Factor ◽

Replication Crisis ◽

Visual Motor

Abstract Purpose The "replication crisis" in psychology and across the broader field of social sciences raises criticism due to a lack of data to show that esoteric research findings can be replicated. The present study replicated and validated the two-factor “memory” and “speed” structure of ImPACT (Schatz & Maerlender, 2013). Methods High school aged athletes (N=18,918, Mean age=15.4, SD=1.2) who completed pre-season baseline ImPACT testing were randomly assigned to one of 5 independent samples of approximately 3,780 athletes. Exploratory factor analyses (FA) for a two-factor solution were conducted with ImPACT composite scores within each of the five groups. Post-Concussion Symptom Scale (PCSS) scores were included, with the expectation they would load on a third, unique factor. Results All five samples met assumptions for FA (KMO Measure of Sampling Adequacy above .600), and all five analyses yielded the same “memory” and “speed” two-factor structure. Visual Motor Speed and Reaction Time loaded on the first "Speed" factor and Verbal and Visual Memory loaded on a second "Memory" factor. The PCSS scores loaded on a third, unique “symptom” factor. Conclusion Replication of the two-factor structure for ImPACT in a five large high school sample further validates the model. Given that both visual and verbal memory involve encoding of information presented visually, use of a “memory” factor may improve interpretation of ImPACT scores. Similarly, similarities between constructs measuring speed of responding (Reaction Time) and speed of processing (Visual Motor Processing Speed) may be best explained using a “speed” factor.

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