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Concise Accounts Dr Sanjay Manohar University of Cambridge 2001 University of Oxford 2015 http://www.smanohar.com Eye movements S Superior, uperior, inferior inferior rectus rectus Look Look up up & & down down S Superior, uperior, inferior inferior oblique oblique Intorsion, Intorsion, extorsion extorsion Mechanism Lateral, Lateral, medial medial rectus rectus Abduction, Abduction, adduction adduction Purpose Direct the high-acuity fovea towards important areas Stabilise retinal image; slight movements to prevent adaptation Eye movements Fixation movements Tremor Drift Non-fixation movements Microsaccades Conjunct Disjunct Image stabilising Saccades OKR VOR Vergence SP Olfaction Receptors Nonspecific to single odorants (vertebrates) cAMP coupled to cation channel Bulb Convergence is spatially organised Processing reverses non-specificity of receptors contralateral contralateral PPiriform iriformcortex cortex Amygdala Amygdala Entorhinal Entorhinal cortex cortex anterior anterior commisure commisure mitral mitral cell cell glomerulus glomerulus receptor receptor granule granulecell cell AMPA modification Discovered by Bass & Weintraub (1987) • 4 or 5 subunits, hetromeric • Most in brain contain GluR2 subunit • Post-transcriptional modification in ~90% – – – – mRNA has arginine codon adenosine ® inosine (similar to thymidine) by adenosine deaminase (ADAR) arginine ® glutamine codon • Channel becomes Ca++ impermeable • So only Na+ and K+ permeable Visual acuity • Definition – = 2 point discrimination = resolution – Measured as angle (e.g. 45 arcseconds) • Target – contrast, colour, luminance • Optical point spread – lens • chromatic, spherical aberration • myopia, hypermetropia, presbyopia – glare, pupillary diffraction • Neural – receptor spacing – pooling
