Transcranial focused ultrasound (tFUS) is a non-invasive neurostimulation modality capable of targeting deep brain regions with high spatial resolution. Despite its growing popularity, there is still a need to investigate the direct effect of its focused mechanical waves on the activation of the neuronal populations in specific brain areas in addition to the role that each of its physical parameters plays in this process. For this purpose, we have used fluorescent calcium imaging with fiber photometry to visualize the changes in the neuronal activity upon stimulation with tFUS. Fiber photometry allows live observation of fluorescence variations in response to changing several physical parameters of tFUS like peak negative pressure (PNP), pulse repetition frequency (PRF), and pulse duration (PD), as well as other experimental parameters like the level of anesthesia. In this work, we have been able to overcome the technical challenge of targeting with tFUS the same brain region where a fiber optic cannula is implanted. An angled implantation approach was adopted to enable monitoring the fluorescent calcium fluctuations in the infralimbic cortex of adult mice upon normally stimulating it with a single element transducer. Critical variations in neuronal population activity were identified in response to tFUS pulses, with these variations dependent on the different physical and experimental parameters. Our study provides a novel methodology for using fiber photometry as a reliable readout in the assessment of the direct effects of ultrasound waves on the variations of neuronal activity.