The Geriatric Nutritional Risk Index is a prognostic marker in patients with metastatic colorectal cancer.

BACKGROUND: The Geriatric Nutritional Risk Index (GNRI) is a nutritional index for elderly patients that is associated with prognosis in cancer patients. We investigated using the GNRI in patients with metastatic colorectal cancer to predict prognosis. METHODS: This study included 419 metastatic colorectal cancer patients who received first-line chemotherapy between February 2005 and December 2020. First, we calculated pre-treatment GNRI and divided the patients into four groups according to the values (G1-G4). We evaluated patient characteristics and overall survival in the four groups. RESULTS: Overall, 419 patients were included. The median follow-up was 34.4 months. Lower GNRI was positively associated with a lower grade Eastern Cooperative Oncology Group Performance Status (p = 0.009), synchronous metastases (p < 0.001), primary tumor resection prior to chemotherapy (p = 0.006), and did not undergo resection after chemotherapy (p < 0.001). Patients with low GNRI had significantly shorter overall survival than the group with high GNRI (median OS: G1 = 19.3 months [M], G2 = 30.8 M, G3 = 38 M, G4 = 39.7 M; log-rank test, p < 0.001). Multivariate Cox regression analysis showed that GNRI was an independent prognostic factor (G3: HR = 0.49, 95% CI = 0.35-0.69; G4: HR = 0.67, 95% CI = 0.48-0.93). In the subgroup analysis of overall survival, we found no interaction between clinicopathological factors and the prognostic value of GNRI. Interestingly, younger patients (< 70 years) but not older patients showed a significant difference in overall survival according to GNRI, despite being the metric being designed for elderly patients. CONCLUSION: Pretreatment GNRI can be a prognostic marker for patients with mCRC who received systemic chemotherapy.

Prognostic Significance of Systemic Inflammation Indices by K-ras Status in Patients With Metastatic Colorectal Cancer.

BACKGROUND: Systemic inflammation markers are useful prognostic indicators for metastatic colorectal cancer. However, the influence of K-ras genotypes on these markers in patients with metastatic colorectal cancer is unclear. OBJECTIVE: This study aimed to evaluate the associations between systems of evaluating pretreatment systemic inflammation and outcomes according to K-ras genotypes in patients with metastatic colorectal cancer. DESIGN: This was a retrospective study. SETTINGS: This study was conducted at a university hospital. PATIENTS: This study included a total of 272 patients ( K-ras wild type: K-ras mutant = 169:103) who received first-line systemic chemotherapy for metastatic colorectal cancer. MAIN OUTCOME MEASURES: We retrospectively calculated 8 systemic inflammation indices: neutrophil/lymphocyte ratio, platelet/lymphocyte ratio, lymphocyte/monocyte ratio, prognostic nutritional index, Glasgow prognostic score, Naples prognostic score, systemic inflammation score, and systemic immune-inflammation index. Patients were categorized into high or low groups for each index. The prognostic relevance of these indices for overall survival was evaluated according to the K-ras genotype. RESULTS: Kaplan-Meier survival analyses showed that median overall survival significantly differed between the high and low groups for all indices in the K-ras wild-type group but not in the K-ras mutant group, except for Glasgow prognostic score and lymphocyte/monocyte ratio. Multivariate Cox regression analyses identified all indices as independent prognostic factors. In the K-ras wild-type group, all indices except platelet/lymphocyte ratio had strong prognostic effects, but not in the K-ras mutant group. Interaction tests indicated that K-ras genotype significantly influenced the prognostic impacts of the neutrophil/lymphocyte ratio ( p = 0.042), prognostic nutritional index ( p = 0.048), Naples prognostic score ( p < 0.001), and systemic immune-inflammation index ( p = 0.004). LIMITATIONS: A major limitation of this study is the lack of external validation. CONCLUSIONS: The prognostic significance of systemic inflammation indices is more useful in patients with K-ras wild-type metastatic colorectal cancer than those with K-ras mutant cancer. See Video Abstract at http://links.lww.com/DCR/B921 . IMPORTANCIA PRONSTICA DE LOS NDICES DE INFLAMACIN SISTMICA POR ESTADO DE KRAS EN PACIENTES CON CNCER COLORRECTAL METASTSICO: ANTECEDENTES:Los marcadores de inflamación sistémica son indicadores de pronósticos útiles para el cáncer colorrectal metastásico. Sin embargo, la influencia de los genotipos KRAS en estos marcadores en pacientes con cáncer colorrectal metastásico no está clara.OBJETIVO:Evaluamos las asociaciones entre los sistemas de evaluación de la inflamación sistémica previa al tratamiento y los resultados según los genotipos K-ras en pacientes con cáncer colorrectal metastásico.AJUSTE:Este estudio se realizó en un hospital universitario.DISEÑO:Este fue un estudio retrospectivo.PACIENTES:Un total de 272 pacientes (K-ras wildtype [K-raswt]:mutant [K-rasMut] = 169:103) que recibieron quimioterapia sistémica de primera línea para el cáncer colorrectal metastásico.PRINCIPALES MEDIDAS DE RESULTADO:Calculamos retrospectivamente 8 índices de inflamación sistémica: proporción de neutrófilos/linfocitos, proporción de plaquetas/linfocitos, proporción de linfocitos/monocitos, índice nutricional pronóstico, puntuación de pronóstico de Glasgow, puntuación de pronóstico de Nápoles, puntuación de inflamación sistémica e índice de inmunoinflamación sistémica. Los pacientes se clasificaron en grupos altos o bajos para cada índice. La relevancia pronóstica de estos índices para la supervivencia global se evaluó según el genotipo K-ras.RESULTADOS:Los análisis de supervivencia de Kaplan-Meier mostraron que la mediana de la supervivencia general difería significativamente entre los grupos alto y bajo para todos los índices en el grupo K-raswt pero no en el grupo K-rasMut, excepto para la puntuación de pronóstico de Glasgow y la proporción de linfocitos/monocitos. Los análisis de regresión multivariable de Cox identificaron todos los índices como factores pronósticos independientes. En el grupo K-raswt, todos los índices, excepto el cociente plaquetas/linfocitos, tuvieron fuertes efectos pronósticos, pero no en el grupo K-rasMut. Las pruebas de interacción indicaron que el genotipo K-ras influyó significativamente en los impactos pronósticos de la proporción de neutrófilos/linfocitos (p = 0,042), el índice nutricional pronóstico (p = 0,048), la puntuación pronóstica de Nápoles (p < 0,001) y el índice de inflamación inmunológica sistémica (p = 0,004).LIMITACIÓN:Una limitación importante de este estudio es la falta de validación externa.CONCLUSIÓNES:La importancia pronóstica de los índices de inflamación sistémica es más útil en pacientes con cáncer colorrectal metastásico K-raswt. Consulte Video Resumen en http://links.lww.com/DCR/B921 . (Traducción-Dr. Yolanda Colorado ).

Rectal cancer diagnosed after resection of isolated brain metastasis.

BACKGROUND: Brain metastasis of colorectal cancer is infrequent, and isolated brain metastases are more infrequent. Thus, when neurological symptoms, such as paralysis or disturbance of consciousness appear, there is a high probability that the cancer has spread to other organs. CASE PRESENTATION: Here, we present a 64-year-old man with a progressive headache, decreased motivation, and aphasia who was diagnosed with a brain tumor in the left frontal region. He underwent a craniotomy, and the brain tumor was diagnosed as adenocarcinoma. We performed a colonoscopy and diagnosed rectal cancer without other distant metastases. After whole-brain radiotherapy (WBRT), low anterior resection for primary rectal tumor was performed using a robotic system. The patient was discharged in good condition and received postoperative adjuvant therapy for rectal cancer. He showed no signs of recurrence after 1 year of follow-up. CONCLUSIONS: We described a rare case of rectal cancer that was diagnosed after resection of isolated brain metastasis. A good prognosis was achieved with surgery and WBRT.

Overall survival after recurrence in stage I-III colorectal cancer patients in accordance with the recurrence organ site and pattern.

AIM: This study aimed to investigate the prognosis after recurrence in patients with stage I-III colon cancer (CC) and rectal cancer (RC). METHODS: Cancer recurred in 116 (15.2%) out of 763 patients with stage I-III colorectal cancer. The overall survival (OS) after recurrence was evaluated based on the recurrence organs and patterns. RESULTS: The first recurrence occurred in the lungs, livers, lymph nodes, and other sites in 32, 22, 12, and 2 patients, respectively. It was localized, disseminated, and involved two or more organs in 14, 9, and 25 patients, respectively. Patients with CC had a shorter OS after recurrence as compared to those with RC (P = .0103). Compared to other organ metastasis, liver metastasis was associated with an earlier recurrence (P = .0026) and shorter OS after recurrence (hazard ratio [HR]: 2.216; 95% confidence interval [CI]: 1.052-4.459; P = .0370). Lung metastasis was associated with a more favorable prognosis as compared to other organ recurrences (HR: 0.338; 95% CI: 0.135-0.741; P = .0057). One-organ recurrence and oligometastasis were observed in 78.4% and 49.1% of the patients, respectively. The 5-y OS rates of patients with one-organ recurrence and oligometastasis were 47.5% and 71.7%, respectively. Invasive treatment was associated with a favorable prognosis (P < .0001). CONCLUSIONS: Liver metastasis and dissemination were associated with a shorter OS after recurrence. Approximately 50% of the patients experienced oligometastasis, which was associated with a favorable prognosis. Hence, to improve patient prognosis it is better to perform invasive treatments when possible.

Relapse of Rectal Cancer in an Anal Fistula: A Rare Case.

BACKGROUND: Colorectal cancer is the second most common cause of cancer-related death worldwide. It is well-known that metasta sis to the liver and lung and local recurrences can occur. Additionally, colorectal cancer occasionally metastasizes to other sites. Only a few reports of such metastases have been published and no definitive therapeutic strategies have been proposed for them. CASE REPORT: The case of a 77-year-old man who was diagnosed with rectal cancer is presented. Eighteen months after curative laparoscopic low anterior resection and D3 lymph node resection, an anal fistula metastasis was diagnosed by computed tomography and biopsy. After administering radiotherapy, percutaneous excision of the lesion. was performed. At 21 months from the surgery, the patient is healthy and no recurrence has been found. CONCLUSION: Metachronous metastasis of a colorectal cancer to an anal fistula is rare. Careful investigation and optimal treatment can result in a disease-free status.

Visual instrumental learning in blindsight monkeys.

Blindsight is the residual visuo-motor ability without subjective awareness observed after lesions of the primary visual cortex (V1). Various visual functions are retained, however, instrumental visual associative learning remains to be investigated. Here we examined the secondary reinforcing properties of visual cues presented to the hemianopic field of macaque monkeys with unilateral V1 lesions. Our aim was to test the potential role of visual pathways bypassing V1 in reinforcing visual instrumental learning. When learning the location of a hidden area in an oculomotor search task, conditioned visual cues presented to the lesion-affected hemifield operated as an effective secondary reinforcer. We noted that not only the hidden area location, but also the vector of the saccade entering the target area was reinforced. Importantly, when the visual reinforcement signal was presented in the lesion-affected field, the monkeys continued searching, as opposed to stopping when the cue was presented in the intact field. This suggests the monkeys were less confident that the target location had been discovered when the reinforcement cue was presented in the affected field. These results indicate that the visual signals mediated by the residual visual pathways after V1 lesions can access fundamental reinforcement mechanisms but with impaired visual awareness.

A case of primary carcinosarcoma of the liver with combined hepatocellular carcinoma and cholangiocarcinoma.

Primary carcinosarcoma of the liver is extremely rare. Here, we report an unusual case of carcinosarcoma of the liver containing combined hepatocellular carcinoma and cholangiocarcinoma. A 66-year-old man with a history of viral hepatitis B was admitted for investigation of multiple liver masses. Dynamic computed tomography revealed a mostly hypoenhancing main tumor with a peripheral ring enhancement and several satellite nodules. After transcatheter arterial chemoembolization and portal vein embolization, an extended right posterior sectionectomy was performed. The resected tumor was macroscopically a simple nodular type, 4.3 × 4.2 cm in diameter, with a dense fibrous capsule. The pathological findings showed that both carcinomatous and sarcomatous elements were present, and diagnosis of carcinosarcoma of the liver was confirmed. The carcinomatous element consisted of hepatocellular carcinoma and cholangiocarcinoma. The sarcomatous element was composed of spindle cells. Immunohistochemical studies demonstrated that cytokeratin AE1/AE3, human serum albumin, cytokeratin 7, and Arginase-1 were partially positive in tumor cells of the carcinomatous element but not in tumor cells of the sarcomatous element. Follow-up for 30 months after surgery has shown no signs of recurrence.

Preoperative iron status is a prognosis factor for stage II and III colorectal cancer.

BACKGROUND: Iron deficiency anemia is represented in colorectal cancer (CRC) patients. Iron surplus load to increase non-transferrin bound iron (NTBI), and NTBI promotes cancer progression and influences microbiota. This study investigated whether preoperative serum iron status was associated with prognosis after CRC resection. METHODS: We evaluated preoperative iron and transferrin saturation (TSAT), which was calculated as iron divided by total iron-binding capacity, in 327 patients who underwent surgery for Stage II-III CRC. Fe < 60 µg/dl and TSAT > 40% were defined as low and high iron, respectively. The associations between iron status and overall survival (OS) were evaluated in univariate and multivariate Cox proportional hazards analysis. RESULTS: Of the 327 patients, 179 (54.7%), 124 (37.9%) and 24 (7.3%) had low, normal and high iron, respectively. In univariate analysis, low iron was associated with shorter OS (hazard ratio [HR] 2.821, 95% confidence interval [CI] 1.451-5.485, P = 0.002). High iron was also associated with shorter OS (HR 3.396, 95% CI 1.359-8.489, P = 0.009). In multivariate analysis, high age (P = 0.002), depth of invasion pT4 (P = 0.012), lymph-node metastasis presence (P = 0.035), low albumin (P = 0.011), low iron (HR 2.282, 95% CI 1.163-4.478, P = 0.016) and high iron (HR 3.757, 95% CI 1.486-9.494 P = 0.005) were independently associated with shorter OS. High iron was associated with the amount of intratumoral Fusobacterium nucleatum compared with normal iron. CONCLUSION: Both low and high preoperative iron in Stage II-III CRC patients were associated with unfavorable OS in univariate and multivariate analyses.

Preoperative transferrin level is a novel prognostic marker for colorectal cancer.

AIM: This study investigated whether preoperative serum transferrin, a rapid-turnover protein, was associated with prognosis after colorectal cancer (CRC) resection. METHODS: We evaluated preoperative transferrin, which was calculated as iron and unsaturated iron-binding capacity, in 501 patients who underwent surgery for Stage I-III CRC. Transferrin level was directly proportional to total iron-binding capacity (TIBC), and TIBC < 250 µg/dl was defined as low transferrin. The associations between transferrin and prognosis were evaluated in univariate and multivariate Cox proportional hazards analyses. RESULTS: Fifty-eight of 501 patients (11.5%) had low transferrin. In these patients, low transferrin was significantly associated with high age, female gender, low body mass index (<18.5), high white blood cell count, low total protein, low albumin, high C-reactive protein, low hemoglobin, and low neutrophil/lymphocyte ratio. In the univariate analysis, low transferrin was associated with shorter relapse-free survival (RFS) (hazard ratio [HR] 2.180, 95% confidence interval [CI] 1.417-3.354, P < .001), overall survival (OS) (HR 2.930, 95% CI 1.784-4.811, P < .001), and cancer-specific survival (CSS) (HR 2.122, 95% CI 1.053-4.275, P = .035). In multivariate analysis, high age (P < .001), Glasgow Prognostic Score (P = .009), and low transferrin (HR 2.336, 95% CI 1.173-4.654, P = .011) were independently associated with shorter OS, and depth of invasion pT4 (P = .015), presence of lymph node metastasis (P = .001), low hemoglobin (P = .034), and low transferrin (HR 2.638, 95% CI 1.113-5.043, P = .025) were independently associated with shorter CSS. CONCLUSIONS: Preoperative serum transferrin in Stage I-III CRC patients was identified as a novel prognostic marker by univariate and multivariate analyses.

The posterior parietal cortex contributes to visuomotor processing for saccades in blindsight macaques.

Patients with damage to the primary visual cortex (V1) lose visual awareness, yet retain the ability to perform visuomotor tasks, which is called "blindsight." To understand the neural mechanisms underlying this residual visuomotor function, we studied a non-human primate model of blindsight with a unilateral lesion of V1 using various oculomotor tasks. Functional brain imaging by positron emission tomography showed a significant change after V1 lesion in saccade-related visuomotor activity in the intraparietal sulcus area in the ipsi- and contralesional posterior parietal cortex. Single unit recordings in the lateral bank of the intraparietal sulcus (lbIPS) showed visual responses to targets in the contralateral visual field on both hemispheres. Injection of muscimol into the ipsi- or contralesional lbIPSs significantly impaired saccades to targets in the V1 lesion-affected visual field, differently from previous reports in intact animals. These results indicate that the bilateral lbIPSs contribute to visuomotor function in blindsight.

Interval laparoscopic appendectomy after antibiotic therapy for appendiceal abscess in elderly patients.

INTRODUCTION: The aim of this study was to evaluate the safety and efficacy of interval laparoscopic appendectomy after antibiotic therapy in elderly patients with appendiceal abscess. METHODS: We retrospectively analyzed data for 50 patients with appendiceal abscess aged ≥18 years who had initially planned to undergo interval laparoscopic appendectomy after antibiotic therapy and 50 patients with appendicitis aged ≥70 years who had undergone early laparoscopic appendectomy. All patients were treated at the National Hospital Organization Kumamoto Medical Center between 2012 and 2018. We compared perioperative outcomes after interval appendectomy between patients aged <70 years and ≥70 years. RESULTS: Clinical progression of appendicitis during antibiotic therapy developed in one patient (2.0%), and recurrent appendicitis after antibiotic therapy for appendiceal abscess occurred in two patients (4.0%). Pathological findings confirmed appendiceal neoplasms in four patients (8.0%). Postoperative infectious complications occurred in 1 of 47 patients (2.1%) who had undergone successful interval laparoscopic appendectomy, and the median length of postoperative hospital stay was 4 days (interquartile range, 3-5 days). There were no significant differences in outcomes after interval appendectomy between patients aged <70 years and ≥70 years. In the secondary analysis, the median length of postoperative hospital stay after interval laparoscopic appendectomy for appendiceal abscess (4 days) was significantly shorter than that after early laparoscopic appendectomy for uncomplicated appendicitis (7 days; P < .001). CONCLUSIONS: Interval laparoscopic appendectomy for appendiceal abscess may be safe and effective in elderly patients without severe comorbidities. Interval appendectomy may be necessary for determining the underlying cause of appendiceal abscess in adults.

Dissecting the circuit for blindsight to reveal the critical role of pulvinar and superior colliculus.

In patients with damage to the primary visual cortex (V1), residual vision can guide goal-directed movements to targets in the blind field without awareness. This phenomenon has been termed blindsight, and its neural mechanisms are controversial. There should be visual pathways to the higher visual cortices bypassing V1, however some literature propose that the signal is mediated by the superior colliculus (SC) and pulvinar, while others claim the dorsal lateral geniculate nucleus (dLGN) transmits the signal. Here, we directly test the role of SC to ventrolateral pulvinar (vlPul) pathway in blindsight monkeys. Pharmacological inactivation of vlPul impairs visually guided saccades (VGS) in the blind field. Selective and reversible blockade of the SC-vlPul pathway by combining two viral vectors also impairs VGS. With these results we claim the SC-vlPul pathway contributes to blindsight. The discrepancy would be due to the extent of retrograde degeneration of dLGN and task used for assessment.

Laparoscopic removal of an ingested fish bone that penetrated the stomach and was embedded in the pancreas: a case report.

BACKGROUND: The gastrointestinal tract can occasionally be perforated or penetrated by an ingested foreign body, such as a fish bone. However, there are very few reported cases in which an ingested fish bone penetrated the gastrointestinal tract and was embedded in the pancreas. CASE PRESENTATION: An 80-year-old male presented with epigastric pain. Computed tomography of the abdomen showed a linear, hyperdense, foreign body that penetrated through the posterior wall of the gastric antrum. There was no evidence of free air, abscess formation, migration of the foreign body into the pancreas, or pancreatitis. As the patient had a history of fish bone ingestion, we made a diagnosis of localized peritonitis caused by fish bone penetration of the posterior wall of the gastric antrum. We first attempted to remove the foreign body endoscopically, but failed because it was not detected. Hence, an emergency laparoscopic surgery was performed. A linear, hard, foreign body penetrated through the posterior wall of the gastric antrum and was embedded in the pancreas. The foreign body was safely removed laparoscopically and was identified as a 2.5-cm-long fish bone. Intraperitoneal lavage was performed, and a drain was placed in the lesser sac. The patient recovered without complications and was discharged on the 7th postoperative day. CONCLUSION: Laparoscopic surgery could be performed safely for the removal of an ingested fish bone embedded in the pancreas.

Emergence of visually-evoked reward expectation signals in dopamine neurons via the superior colliculus in V1 lesioned monkeys.

Responses of midbrain dopamine (DA) neurons reflecting expected reward from sensory cues are critical for reward-based associative learning. However, critical pathways by which reward-related visual information is relayed to DA neurons remain unclear. To address this question, we investigated Pavlovian conditioning in macaque monkeys with unilateral primary visual cortex (V1) lesions (an animal model of 'blindsight'). Anticipatory licking responses to obtain juice drops were elicited in response to visual conditioned stimuli (CS) in the affected visual field. Subsequent pharmacological inactivation of the superior colliculus (SC) suppressed the anticipatory licking. Concurrent single unit recordings indicated that DA responses reflecting the reward expectation could be recorded in the absence of V1, and that these responses were also suppressed by SC inactivation. These results indicate that the subcortical visual circuit can relay reward-predicting visual information to DA neurons and integrity of the SC is necessary for visually-elicited classically conditioned responses after V1 lesion.

Residual attention guidance in blindsight monkeys watching complex natural scenes.

Patients with damage to primary visual cortex (V1) demonstrate residual performance on laboratory visual tasks despite denial of conscious seeing (blindsight) [1]. After a period of recovery, which suggests a role for plasticity [2], visual sensitivity higher than chance is observed in humans and monkeys for simple luminance-defined stimuli, grating stimuli, moving gratings, and other stimuli [3-7]. Some residual cognitive processes including bottom-up attention and spatial memory have also been demonstrated [8-10]. To date, little is known about blindsight with natural stimuli and spontaneous visual behavior. In particular, is orienting attention toward salient stimuli during free viewing still possible? We used a computational saliency map model to analyze spontaneous eye movements of monkeys with blindsight from unilateral ablation of V1. Despite general deficits in gaze allocation, monkeys were significantly attracted to salient stimuli. The contribution of orientation features to salience was nearly abolished, whereas contributions of motion, intensity, and color features were preserved. Control experiments employing laboratory stimuli confirmed the free-viewing finding that lesioned monkeys retained color sensitivity. Our results show that attention guidance over complex natural scenes is preserved in the absence of V1, thereby directly challenging theories and models that crucially depend on V1 to compute the low-level visual features that guide attention.

Contribution of the retino-tectal pathway to visually guided saccades after lesion of the primary visual cortex in monkeys.

Previous reports on 'blindsight' have shown that some patients with lesions of the primary visual cortex (V1) could localize visual targets in their scotoma with hand and/or eye movements without visual awareness. A role of the retino-tectal pathway on residual vision has been proposed but the direct evidence for this still remains sparse. To examine this possibility, we inactivated the superior colliculus (SC) of unilateral V1-lesioned monkeys using microinjections of muscimol, and analysed the effects on visually guided saccades. Following muscimol injections into the contralesional SC, the monkeys performed the visually guided saccade task with relatively minor deficits. The effects of ipsilesional SC inactivation were more severe. After injections, the monkeys failed to localize the target within the visual field represented at the injection site on the SC map. The effects of ipsilesional SC inactivation may result from sensory deficits, motor deficits or a combination of both. To examine these possibilities, we tested the effects of SC inactivation on the motor system by investigating spontaneous saccades. After inactivation of the ipsilesional SC, spontaneous saccades toward the injection site were not abolished, suggesting that impairment of visually guided saccades following inactivation of the ipsilesional SC could not be explained solely by a motor deficit and was primarily due to a visual deficit, presumably by interfering with processing in the superficial layer. We conclude that the retino-tectal pathway plays an essential role in residual vision after V1 lesion. The results suggest that this pathway may be involved in mediating unconscious vision in blindsight patients.

Striate cortical lesions affect deliberate decision and control of saccade: implication for blindsight.

Monkeys with unilateral lesions of the primary visual cortex (V1) can make saccades to visual stimuli in their contralateral ("affected") hemifield, but their sensitivity to luminance contrast is reduced. We examined whether the effects of V1 lesions were restricted to vision or included later stages of visual-oculomotor processing. Monkeys with unilateral V1 lesions were tested with a visually guided saccade task with stimuli in various spatial positions and of various luminance contrasts. Saccades to the stimuli in the affected hemifield were compared with those to the near-threshold stimuli in the normal hemifield so that the performances of localization were similar. Scatter in the end points of saccades to the affected hemifield was much larger than that of saccades to the near-threshold stimuli in the normal hemifield. Additional analysis revealed that this was because the initial directional error was not as sufficiently compensated as it was in the normal hemifield. The distribution of saccadic reaction times in the affected hemifield tended to be narrow. We modeled the distribution of saccadic reaction times by a modified diffusion model and obtained evidence that the decision threshold for initiation of saccades to the affected hemifield was lower than that for saccades to the normal hemifield. These results suggest that the geniculostriate pathway is crucial for on-line compensatory mechanisms of saccadic control and for decision processes. We propose that these results reflect deficits in deliberate control of visual-oculomotor processing after V1 lesions, which may parallel loss of visual awareness in human blindsight patients.

Contribution of GABAergic inhibition to the responses of secondary vestibular neurons to head rotation in the rat.

To assess the contribution of GABAA receptor-mediated inputs in control of vestibular responses of secondary vestibular neurons, we examined the effects of the GABAA receptor antagonists, bicuculline and picrotoxin, on these neurons in anesthetized rats. Horizontal canal-related secondary vestibular neurons were identified by their monosynaptic excitation from the ipsilateral vestibular nerve and by the modulation of their firing rate for head rotation. Responses to sinusoidal head rotation were recorded before and during iontophoretic application of the drugs. Application of bicuculline increased DC level of the responses (mean firing rate in each cycle) in all of the 10 neurons examined. In seven of these, the gain was increased along with the DC level, but the phase was virtually unaffected. Similarly, picrotoxin increased both the DC level (4/4) and the gain (3/4), but did not affect the phase. In the 10 neurons that increased the gain, the mean percent increase in the gain was 31% (8-54%). These results indicate that the majority of neurons received inhibitory inputs that were in phase with the excitatory inputs from primary afferents. This suggests that these neurons received GABAergic input of non-commissural origin, most likely from the flocculus.