Subjects
Pituitary adenomas patients were were recruited in the Department of Neurosurgery, Wuhan School of Clinical Medicine, Southern Medical University (China) during diagnostic hospitalization. The inclusion criteria for patients were as follows: (1) the tumors were pathologically and immunohistochemically diagnosed as pituitary adenoma; (2) No history of craniotomy and radiation therapy; (3) they did not have any severe heart, liver and kidney failure; (4) Participants could cooperate to complete ERPs tests. Exclusion criteria for patients were as follows: (1) A history of neurologic or psychiatric disorders; (2) No drug or alcohol abuse [subjects who drink alcohol over 2.0 standard drinks (10 g of pure alcohol) on days and meet any 2 of the 11 criteria under the DSM-V in the past year] [21], and medication intake (including oral contraceptives). All patients and healthy controls (HCs) had visual acuity and hearing ability sufficient to take part in the test. Cognition evaluation (ERPs study) was conducted to investigate the affective picture processing before the surgery. There were 26 patients that have prolactinoma, growth hormone (GH) pituitary adenoma or non-functional pituitary adenoma separately meeting the above-mentioned conditions (female,15; 27.9±2.8 y). 26 healthy people matched to the patients of observation group with age, sex, education, and handedness (female, 15; 27.2±2.9 y) were selected as the HCs. People in the HCs were in good health, without mental disease and history of psychoactive substance abuse as well as family history of mental illness. There was no significant difference in age, gender, educational level between the two groups (p >0.05). The study was approved by the ethics committee of Wuhan School of Clinical Medicine, Southern Medical University, and informed consents were explained carefully and obtained from all participants.
Radiological assessment
All participants underwent preoperative coronal and sagittal Magnetic Resonance Imaging (MRI) scanning by a 1.5T GE scanner (GE EXCITE, Milwaukee, WI, USA) with a head coil. Participants lied on their back with cushions around their head to inhibit their head motion, and earplugs (29 dB) in their ears to reduce scanner noise. Adenoma and the size were recognized through MRI image by two experienced neurosurgeon blinded to patients’ clinical features. Median adenoma diameter on sagittal imaging was about 21.0mm (mean 21.0 ± 4.4mm). Median suprasellar tumor extension scored 8.4 mm (mean 8.4 ± 3.3 mm). The compression of frontal lobe parenchyma was present in all cases. There were no abnormalities in the MRI image of control people evaluated by the same two neurosurgeons.
Endocrinological assessment
Endocrinological levels on the whole pituitary axes were measured from 8:00 a.m. to 9:30 a.m. on the day of LPP testing considering circadian variation in hormone levels. Clotted or heparinized blood was delivered in ice boxes to the clinical laboratory of Chinese People’s Liberation Army General Hospital of Central War Zone. 14 patients with prolactinomas manifested hyper- prolactin (PRL) soley. 2 patients with prolactinomas were hyper- PRL and hyper-GH. 10 patients with non-functional pituitary adenoma had normal hormonal status. All the 26 people in HCs had normal hormonal levels.
Stimuli and procedure
Sixty pictures were selected from the International Affective Picture System (IAPS) [22]. Visual stimuli used IAPS pictures in the center of a computer screen (light degree = 60 cd/m2). The examinee was seated in a semi-dark room, watching the screen 100 cm from their eyes, with a visual angle of 4°×4°. Stimuli consisted of 20 positive images including babies and animals, 20 neutral images including objects, and 20 negative images including attack scenes, violence, and wild animals. Affective stimuli were matched on arousal (See Table 1). One-way repeated-measures ANOVAs were computed for valence and for arousal dimensions. Post-hoc contrasts indicated that positive stimuli and negative stimuli showed distinct valence but not distinct arousal. Positive stimuli and negative stimuli differed from neutral stimuli both in arousal and valence. The trial began with a fixation mark (+) on the black screen for 1000 ms, and then a random image appeared for 2000 ms. The images were presented in a pseudo-random order, with the constraint that a specific image appeared no more than three times consecutively. One trial contains 45 negative, 45 neutral, and 45 positive stimuli so that one trial takes 405 seconds. The stimulus presentation was controlled with the E-prime (Psychology Software Tools). During the trial, the subjects were instructed to look passively at the pictures, and reduce eye blinks and body movements as much as they can. We just instruct participants to mentally categorize these stimuli and without any pressing button, only in order to pay their attention on these stimuli.
EEG recording and analysis
The electroencephalography (EEG) signals were continuously recorded (band pass 0.05-200Hz, sampling rate 1000Hz) at central- parietal electrode sites (C3, Cz, C4, P3, Pz, P4; 10-20 International System) referenced to the left mastoid (right mastoid as recording site). The EEG data were off-line re-referenced to the bio-mastoids reference. The EEG was from 200 ms pre-stimulus to 800 ms post-stimulus, and the baseline corrected to the mean amplitude 200 ms before the stimulus. The EEG were segmened separately for positive, negative and neutral stimuli. The artifact-free EEG with positive, negative and neutral conditions were averaged respectively and at least 50 trials were available for each subject and condition. For further analysis, the ERPs data were digitally low-pass filtered at 30 Hz (24 dB/octave).
Compared with ERPs induced by neutral stimuli, positive and negative stimuli produced larger parietal LPP, regardless of pituitary adenoma or control group. The measurements of amplitudes of LPP was computed for time windows: 300~550 ms. Analyses were conducted using a 3 (type of stimuli picture: positive, negative and neutral) × 6 (electrode site: C3, Cz, C4, P3, Pz, P4) × 2 (patient group and HCs) repeated-measures analysis of variance (ANOVA) to acquire effects of different stimulus picture and whether these effects are different among the electrode site of the LPP and between the two groups. The degree of freedom was corrected with Greenhouse–Geisser epsilon.